JP2008233915A - Electro-optical switching element and electro-optical display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electro-optical switching element and a display including the same. <P>SOLUTION: The electro-optical switching element contains: a cholesteric liquid crystal being a liquid crystal material containing at least one light emitting part; and an optical component capable of eliminating or reducing selective reflection of the cholesteric liquid crystal. Especially, the electro-optical switching element simultaneously uses a liquid crystal material having a spiral structure as illumination and a reflecting material. The manufacturing method of the electro-optical switching element, an electro-optical displays and their use in devices are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to electro-optic switching elements and their use in electro-optic displays and to these displays. In particular, the present invention relates to an electro-optical switching element using a liquid crystal material having a helical structure, and most particularly to an electro-optical switching element using a liquid crystal material having a helical structure as an illumination and reflection material at the same time. Although the liquid crystal spiral structure is an excellent light emitting and reflecting material due to its naturally formed microresonant structure, its strong selective reflection has been a negative effect of applying the material to flat panel display devices so far. It has become. The present invention solves the low contrast problem for liquid crystal helical structures due to strong selective reflection of ambient light. The resulting electro-optic displays are therefore suitable, for example, for flat panel display devices, although these are also part of the invention.

  Inorganic light emitting diodes are frequently used as light emitting devices. Two grades of these inorganic materials are used as flat electroluminescent displays and flat lamps. The first of these two-class inorganic materials is ZnS, ZnSe, ZnS: Mn, etc., which shines upon collision with accelerated charge carriers having an emission center, and the second of these classes is GaN SiC, CaAs, etc., which shine by recombination of charge carriers injected through the electrodes.

  Non-Patent Document 1 describes an electroluminescence (hereinafter referred to as EL) device using a vapor-deposited organic amorphous film. Such organic EL materials have been developed extensively and are now frequently used, for example, in car indicators and as displays for digital still cameras.

  Furthermore, Patent Document 1 discloses a method for providing polarized light emission. In these methods, the rubbed π-conjugated polymer or the π-conjugated polymer on the rubbed alignment layer is used as the light emitting layer. Another method for achieving polarized emission is described in US Pat. In this document, a mixture of a liquid crystal compound and an organic EL material is coated on a substrate, the mixture is aligned, and then the LC material is polymerized by exposure to UV irradiation. Therefore, the orientation of the compound in the mixture representing the emission of polarized light is fixed. Patent Document 3 describes that polarized light emission can be achieved by applying a high voltage to a smectic liquid crystal phase of a naphthalene derivative or a biphenyl derivative in which a fluorescent dye material is present.

  Patent Document 4 has a light emitting layer between a transparent anode electrode and a metal electrode acting as a mirror and a cathode in order to increase the luminance of the organic light emitting diode device, and cholesteric between the anode and the substrate. A circularly polarized light-emitting electroluminescent device having a liquid crystal layer is suggested. Here, the cholesteric liquid crystal layer transmits circularly polarized light having one of two twist directions and reflects circularly polarized light having one (opposite) twist direction by its selective reflection characteristic. The reflected circularly polarized light is partially changed to the opposite circularly polarized light, and the changed light is transmitted through the cholesteric liquid crystal layer. Thus, the cholesteric liquid crystal layer has good light utilization efficiency and is higher than that of a typical linear polarizer using a dichroic dye. Therefore, in Patent Document 4, the cholesteric liquid crystal layer is used as a high-efficiency polarizer.

  In Patent Document 5, in order to increase the luminance of an organic light emitting diode device, a light emitting layer is included between a transparent anode electrode and a metal electrode acting as a mirror and a cathode, and a cholesteric liquid crystal layer, an anode, and a substrate. A circularly polarized light-emitting electroluminescent device is suggested that includes both dielectric mirrors with alternating layers of different refractive indices in between. The light emitted from the light emitting layer is affected by the microresonance effect by the dielectric mirror, and thus the light utilization efficiency is improved. Again, the cholesteric liquid crystal layer is used as a high efficiency polarizer. Patent Document 5 also describes that the light emitting layer is preferably divided into three regions in order to match the three color regions of the liquid crystal cell (eg, red (R), green (G) and blue (B), briefly RGB)). It is described that each is red, green and blue, each having a pitch of 100 μm or less, and the cholesteric layer is preferably formed corresponding to these three RGB color regions.

U.S. Patent No. 6,057,059 suggests a composition comprising a medium having a chiral, helical liquid crystal phase with a substantially fixed, temperature-independent helical pitch as a circularly polarized electroluminescent device. The liquid crystal phase is composed of calamitic liquid crystal molecules having a luminescent portion, and in the composition, excitation of the luminescent portion causes the medium to emit light in the bandwidth of selective reflection of the liquid crystal phase.
Japanese Patent Application Laid-Open No. 08-306954 International Publication No. 97/07654 Pamphlet Japanese Patent Laid-Open No. 11-241069 JP 2001-244080 A JP 2001-244068 A International Publication No. 2004/003108 Pamphlet Tang et al., Applied Physics Letters, vol. 51, p. 913 ff (1987)

  However, inorganic materials, on the other hand, have the disadvantage that they require a relatively high driving voltage, for example, and have a luminous efficiency that is not high enough for blue. Furthermore, it is extremely difficult to obtain polarized light emission using an inorganic material. On the other hand, with respect to the deposited organic film, on the other hand, since the film quality is very sensitive to processing, it is difficult to obtain a uniform film over a wide area. Therefore, the process window is very small. In addition, it is quite difficult to achieve polarized light emission from the amorphous organic film.

  With respect to π-conjugated polymers, the conventional rubbing process only aligns a very thin surface layer of the polymer film. At a temperature higher than their glass transition temperature, the π-conjugated polymer is aligned on the rubbed alignment layer in the rubbing direction. However, due to the relatively high viscosity, this process is very slow and the degree of orientation is largely very poor. Therefore, its low brightness is also a problem.

  By simply using the cholesteric liquid crystal layer described in Patent Document 4 as a high-efficiency polarizer, high brightness cannot be obtained. Although the use of the microresonance effect described in Patent Document 5 and Patent Document 6 improves the brightness, these electroluminescent devices have the following problems. Most important is the very low contrast ratio obtained when applying cholesteric liquid crystal layers to flat panel display devices for direct view. Since the selective reflection layer of cholesteric liquid crystal is very strong, when the device is in the black state, it reflects ambient light and has a relatively low contrast ratio.

  When an electroluminescent device having a cholesteric liquid crystal layer is applied to a backlight for a liquid crystal display device as described in Patent Document 4, Patent Document 5, and Patent Document 6, this low contrast problem is improved. However, there is no clear description of the detailed device structure in the literature. The application of electroluminescent devices to backlights for liquid crystal display devices after attaching a quarter wave plate to change circularly polarized light into light rich in linearly polarized components is very commonly mentioned. It has only been done. When the cholesteric liquid crystal layer is applied to the backlight system, it is even more important to use the reflected light according to the light emitted from the cholesteric liquid crystal layer. This is possible only when the light emitting part is present in the cholesteric liquid crystal layer. The cholesteric liquid crystal layers described in Patent Document 4 and Patent Document 5 do not include any light-emitting portion, and thus light emitted through the cholesteric liquid crystal layer is in the opposite direction to that of light reflected by the cholesteric liquid crystal layer. Have a rotation of.

  The light emitting portion is included in the cholesteric liquid crystal layer described in Patent Document 6. However, there is no description as to what kind of structure combining the backlight unit and the liquid crystal display device improves the light utilization efficiency and at the same time suppresses selective reflection in the black state. The combination of quarter wave plate and linear polarizer and the arrangement of these optical elements is decisive for the result, for example for different liquid crystal electro-optic modes such as VA mode or IPS mode, and also cholesteric This is significantly different for liquid crystal luminescent materials only, i.e. direct view devices without a liquid crystal layer. As a result, flat panel display devices with high brightness and correct contrast ratio have not been realized so far.

  In order to match the three color regions (RGB) of the liquid crystal cell, the light emitting layer is preferably divided into three regions with a pitch of 100 μm or less, red (R), green (G) and blue (B), preferably these The formation of cholesteric layers corresponding to three RGB color regions is also described. However, the problem of color mixing caused by misalignment between the liquid crystal display device and the electroluminescent device cannot be solved only by processing the light emitting layer at a pitch of 100 μm or less. Furthermore, even when the alignment between the liquid crystal display device and the electroluminescent device is performed very accurately, the problem of parallax caused by the thickness of the substrate cannot be solved only by processing the light emitting layer at a pitch of 100 μm or less. .

The present invention
A cholesteric liquid crystal including at least one light-emitting portion; and an electro-optical switching element including an optical component capable of removing or reducing selective reflection of the cholesteric liquid crystal.
Preferably, the cholesteric liquid crystal includes one or more light emitting moieties.

One or more light-emitting moieties are optionally present in the cholesteric liquid crystal, but one or more separate ones dissolved in the molecules of the liquid crystal material itself or in parts of these molecules or in it. It may be present in the compound. Preferably, one or more light emitting moieties present in the cholesteric liquid crystal are present in one or more of the molecules of the cholesteric liquid crystal material itself.
The cholesteric liquid crystal may be a low molecular weight material or a polymer material. Preferably it is a low molecular weight material.

  In another preferred embodiment of the invention, the cholesteric liquid crystal is a polymeric material obtained or obtainable from a polymerizable liquid crystal (LC), also known as a reactive mesogen (RM).

  The present invention also relates to an electro-optic switching element comprising a cholesteric liquid crystal having a helical pitch that preferably matches the optical path length of the light emitted from the light emitting portion. Usually, the bandwidth of selective reflection is about 100 nm (half width, FWHM), and the wavelength of emitted light is preferably within this bandwidth. The bandwidth of selective reflection depends on the state of formation of the cholesteric liquid crystal and the material itself. However, it is generally accepted that the wavelength of the emitted light is within the selective reflection bandwidth.

Furthermore, the present invention is preferably an optical component that can remove or reduce selective reflection, preferably,
An electro-optic comprising an optical component having one angle that is essentially a Brewster angle or more than one angle that is essentially a Brewster angle, and an optical component capable of converting linearly polarized light into circularly polarized light The present invention relates to a switching element.

  In the present application, the term “a structure having one angle that is essentially Brewster's angle or more than one angle that is essentially Brewster's angle”, unless expressly stated otherwise, This is abbreviated as “a structure having one or more Brewster angles”.

  Here, the tolerance of the angle actually used as the Brewster angle from the theoretically calculated exact value of the Brewster angle depends on the required contrast ratio. The reflection of p-polarized light, that is, polarized light having a vector of an electric field that oscillates parallel to the incident surface at the incident surface is considerably small as an angle close to the theoretically calculated exact value of the Brewster angle. Deviations of several degrees from the theoretically calculated exact value of the Brewster angle, typically in the range + 4 ° to −8 °, preferably in the range + 2 ° to −5 °, and most preferably from + 1 ° to −3 ° is accepted, and as a result, the actual angle used is preferably within these ranges around the theoretically calculated exact value of the Brewster angle.

The present invention also relates to the electro-optic switching element, wherein the optical component capable of removing or reducing the selective reflection of the cholesteric liquid crystal includes a polymer layer.
Furthermore, the present invention provides an optical component capable of removing or reducing selective reflection of cholesteric liquid crystal,
-Including a liquid crystal layer,
A polarizer is not included between the cholesteric liquid crystal and the liquid crystal layer, and an optical component on the opposite side of the liquid crystal layer from the cholesteric liquid crystal layer (the optical component can convert circularly polarized light into linearly polarized light), and the essence A polarizer having a transmission axis parallel to the electric field plane of linearly polarized light,
The present invention relates to the electro-optic switching element.

Further, according to the present invention, the liquid crystal layer of the optical component capable of removing or reducing the selective reflection of the cholesteric liquid crystal has the following alignment-twisted nematic,
The present invention relates to the electro-optical switching element, which is a liquid crystal layer selected from one having hybrid alignment nematic or vertical alignment nematic.
Furthermore, the present invention provides an optical component capable of removing or reducing selective reflection of cholesteric liquid crystal,
-Including a liquid crystal layer,
-An optical component is included on the side facing the cholesteric liquid crystal layer capable of converting circularly polarized light having the same twist direction as the cholesteric liquid crystal layer into linearly polarized light, and-the transmission axes sandwiching the liquid crystal layer are perpendicular to each other Including two linear polarizers and a transmission axis of the polarizer close to a cholesteric liquid crystal layer parallel to the electric field plane of linearly polarized light converted from circularly polarized light,
The present invention relates to the electro-optic switching element.

Further, according to the present invention, the optical component liquid crystal layer capable of removing or reducing the selective reflection of the cholesteric liquid crystal is a liquid crystal layer of the following group: an in-plane switching type liquid crystal layer,
-Fringe field switching liquid crystal layer,
The electro-optical switching element according to claim 7, which is a liquid crystal layer selected from a ferroelectric liquid crystal layer or a ferroelectric liquid crystal polymer.
Furthermore, the present invention relates to the electro-optical switching element, wherein a gap between the cholesteric liquid crystal and the optical component capable of removing or reducing selective reflection of the cholesteric liquid crystal is 0.1 mm or less.

The present invention also relates to the electro-optic switching element, wherein the total thickness of optical components capable of converting circularly polarized light into linearly polarized light is 0.1 mm or less.
Further, the present invention relates to the electro-optical switching element comprising three light emitting means, each for light emission of one of three of three different wavelengths, each of the three means forming each of three layers. About.

The present invention also relates to the electro-optical switching element including light emitting means having three different regions, each having a different emitter, each for emitting light of three different wavelengths.
Furthermore, the present invention relates to the electro-optic switching element, wherein the three different regions for light emission at three different wavelengths each have an extension of 90.000 μm ² or less.

The present invention also relates to the electro-optical switching element including means for scattering light.
Furthermore, the present invention relates to the electro-optical switching element, wherein the means for scattering light is a sheet having a plurality of regions having a refractive index different from that of the surrounding material.

The present invention also relates to the electro-optical switching element, wherein the light scattering means is a polymer dispersed liquid crystal (PDLC) or includes PDLC.
The present invention further relates to the electro-optic switching element, wherein the polymer dispersed liquid crystal is electrically addressable, preferably for switching between a light scattering state and a transparent state.

The invention also provides that the electrical medium having one angle that is essentially a Brewster angle or more than one angle that is essentially a Brewster angle can act as a means for scattering light. The present invention relates to an optical switching element.
Furthermore, the present invention relates to the electro-optical switching element, wherein at least one surface of a cholesteric liquid crystal containing at least one light emitting portion is covered with a light absorption layer.

The present invention also provides that the side of the cholesteric liquid crystal facing the optical component capable of removing or reducing the selective reflection of the cholesteric liquid crystal is transparent to circularly polarized light having a rotation opposite to the twist direction of the cholesteric liquid crystal. The present invention relates to the electro-optical switching element covered with no layer.
Furthermore, the present invention relates to the electro-optical switching element, wherein the layer that is not transparent to circularly polarized light having a rotation opposite to the twist direction of the cholesteric liquid crystal is a half mirror.

In the present invention, the layer that is not transparent to circularly polarized light having a rotation opposite to the twisted direction of the cholesteric liquid crystal comprises a linear polarizer in which at least one surface is covered with a quarter-wave plate. The present invention relates to the electro-optic switching element.
Furthermore, the present invention relates to the electro-optic switching element, wherein the linear polarizer is a wire grid.

The invention also relates to the use of the electro-optic switching element for display information.
The invention further relates to the use of the electro-optic switching element in an electro-optic display.

The present invention also relates to an electro-optic display including one or more electro-optic switching elements.
The present invention further relates to a display device comprising one or more electro-optic displays.

The invention also relates to the use of said electro-optic display for display information.
Furthermore, the present invention is a method of manufacturing a film or plate having a structure having one or more Brewster angles having subunits, wherein the subunits are constructed so as to protrude from a support or a substrate. To the method.

The present invention also relates to a method for manufacturing the electro-optic switching element, characterized in that means for removing or reducing selective reflection of the cholesteric liquid crystal is incorporated.
Furthermore, the present invention relates to a method for manufacturing the electro-optic display, characterized in that means for removing or reducing the selective reflection of the cholesteric liquid crystal is incorporated.

  According to the present invention, the electro-optic switching element provides removal or at least reduction of selective reflection from the cholesteric liquid crystal. When applying cholesteric liquid crystals to light emitting devices, they reflect ambient light very efficiently, and therefore they cannot display a completely black state in the off state. This typically results in a significant reduction in contrast ratio. The present invention, however, provides electro-optic switching elements with high contrast.

  Therefore, the electro-optic switching element of the present invention is beneficially used in flat panel displays. This is also the subject of the present invention, as well as the display devices containing them.

  In a first preferred embodiment of the invention, the electro-optic switching element preferably comprises a film or plate having a structure having one or more Brewster angles and a quarter (λ / 4) wave plate. Contains optical components. By this combination, selective reflection from the cholesteric liquid crystal layer is suppressed, and light emitted from the cholesteric liquid crystal layer is transmitted. As another form of the first preferred embodiment of the present invention, the electro-optic switching element includes a liquid crystal layer instead of the film and the quarter-wave plate, suppresses selective reflection from the cholesteric liquid crystal layer, and reduces the cholesteric liquid crystal layer. Switch the light emitted from.

  The suppression of selective reflection from a cholesteric liquid crystal layer using a film having a structure having one or more Brewster angles and a quarter-wave plate will be described with reference to FIG.

The strongest ambient light, such as sunlight, is expected to enter the device from above. A film 101 having a refractive index n is provided and positioned to tilt θ _B relative to the display surface, where tan (θ _B ) = n. Incident light on the film from above is split into two rays with different polarizations. One ray is the incident plane (p-polarized light, which is light 106 with an electric vector oscillating parallel to). This ray does not reflect. The other ray is light 107 having an oscillating electric vector perpendicular to the incident surface (s-polarized light) and is reflected by the film 101. Only the light 107 reaches the polarizer 102. Here, the transmission axis of the polarizer 102 may be set perpendicular to the vibration direction of the light 107 so that the light 107 cannot enter the polarizer 102. Accordingly, light from above does not reach the cholesteric liquid crystal layer 104. On the other hand, the polarizer 102 and a wide bandwidth (also referred to herein as a quarter-wave plate in the wide wavelength range) so that the circularly polarized light 108 emitted from the cholesteric liquid crystal layer 104 can pass through the polarizer 102. A combination of the quarter-wave plate 103 can be set.

For example, when the cholesteric liquid crystal layer has a counterclockwise twist direction, only the optical axis of the quarter-wave plate 103 is set to an angle of 45 ° that rotates counterclockwise with respect to the transmission axis of the polarizer 102. There must be. Circularly polarized light 108 changes to linearly polarized light and passes through the polarizer 102. It further passes through the membrane 101. Transmission is not 100% at the angle of incidence (90 ° −θ _B ), but the loss due to reflection is generally not significant and is acceptable in most cases because this effect does not reduce the contrast ratio too much. Linearly polarized light then increases the viewing angle and strikes the light scattering film. This display setting suppresses selective reflection from a strong cholesteric liquid crystal layer because light contributing to selective reflection does not reach the cholesteric liquid crystal layer.

  A light absorbing sheet or element can be disposed on the cholesteric liquid crystal layer 104 side opposite to the observation direction in which the polarized light 106 is absorbed. The light absorbing sheet or element may be a black sheet. In FIG. 1, this sheet may be preferably disposed on the cholesteric liquid crystal layer 104 side opposite to the optical elements 103 and 102. In FIG. 1, this is on the right side. Linearly polarized light 106 passes through the combination of linear polarizer 102 and quarter wave plate 103. The cholesteric liquid crystal layer 104 does not reflect this light, but it may be reflected by the outer element. Although this reflected light intensity is not so strong as compared with the light of selective reflection, it is generally preferable to remove it. It is also possible to make the display foldable and stretch it only when in use. Also, an additional light absorbing layer 109 can be used to preferably remove the incident polarized light 106 completely. The additional light absorbing layer 109 may be a black layer as described above. This layer absorbs polarized light 106 that passes through film 101.

In a second preferred embodiment of the present invention, a film having a structure having one or more Brewster angles and a quarter wave plate together from a cholesteric liquid crystal layer as illustrated in FIG. Used to suppress selective reflection. This second aspect of the invention is constructed such that the membrane 201 having a structure having one or more Brewster angles has a plurality of parts or subunits that are constructed to form the Brewster angles. This is different from the first aspect in that it is a device. Preferably, the partial structure has a prismatic shape such as a wedge. These partial structures may preferably protrude from a support or substrate, for example they may be realized on a thin film having a series of wedge shapes as shown in FIG. Preferably, each wedge has a Brewster angle θ _B , where tan (θ _B ) = n, where n is the refractive index of the film. Such films may be prepared using injection molding techniques or UV curing techniques. The narrow side of all the wedges may be oriented in the same direction, or some of the wedges may be oriented in the opposite direction as the others, as shown in FIG.

  Similar to the first preferred embodiment of the present invention, a portion of the polarized ambient light having an electrical vector coming from above and oscillating parallel to the entrance surface 206 is one or more Brewster angles. The other part of the polarized ambient light that has an electrical vector that oscillates parallel to the entrance surface 207 is reflected off the film 201 having a structure with This reflected light cannot pass through the polarizer 202 whose transmission axis is set perpendicular to the vibration direction of the polarized light 207. Therefore, ambient light does not reach the cholesteric liquid crystal layer. Circularly polarized light 208 emitted from the cholesteric liquid crystal layer is changed to linearly polarized light by a quarter-wave plate having a wide bandwidth 203. This light passes through the polarizer 202 and the film 201 having a structure having one or more Brewster angles, and then enters the light scattering film 205 that enhances the viewing angle.

  For flat panel displays that do not require a relatively wide field of view, this light scattering film is optional and may be omitted. When all the narrower portions of the wedge are oriented in one direction, it is possible to place a light absorbing film or element on the structure side having the thicker side of the wedge, as in the first preferred embodiment of the present invention. is there. This display setting suppresses selective reflection from a strong cholesteric liquid crystal layer so that light contributing to selective reflection does not reach the cholesteric liquid crystal layer.

  A third preferred embodiment of the present invention for suppressing selective reflection from a cholesteric liquid crystal layer uses a film comprising a structure having one or more Brewster angles and a quarter wave plate. This aspect will be described below with reference to FIG.

In a third preferred embodiment of the present invention is a membrane structure 310 comprising one or more parts, preferably two or more parts, more preferably a plurality of parts, each comprising two wedges or partial wedges, Preferably two partial wedges or most preferably one wedge and one partial wedge, one of said wedges or partial wedges having an angle that is essentially the Brewster angle θ _B The other uses a different angle α. Preferably, the wedge or partial wedge is realized by superimposing one on top of the other in sequence. A typical implementation of such a structure is shown in FIG. These films are preferably built on a transparent plate or substrate 301. In this specification, the partial wedge means an object having a trapezoidal cross section, that is, a wedge having a tip cut off. Preferably, one surface of these partial wedges is parallel or essentially parallel to the surface of the substrate and / or display, whereas the opposite side is inclined with respect to the first surface. . The remaining two surfaces of the partial wedge cross section are preferably parallel to each other and are preferably orthogonal to the first surface, ie the surface of the substrate and / or the display.

  Preferably, the device or membrane structure of the present invention comprises a plurality of structured regions including two or more sets of substructures. These substructures are preferably wedges or partial wedges, but similar objects may also be used. Hereinafter, throughout this specification, these structures are simply referred to as wedges or partial wedges.

  Preferably, each region of the membrane structure includes two or more wedges or partial wedges. Preferably one or more of the first set of wedges or partial wedges, preferably essentially all and most preferably all wedges or partial wedges, respectively, of the first set of wedges or partial wedges Covered by a second set of wedges or partial wedges or partial wedges at least partially overlapping the wedges or partial wedges. Preferably, the respective wedges or partial wedges of the first and second sets of wedges or partial wedges overlap each other over their entire area. The device or membrane structure of the present invention can also include two or more sets of wedges or partial wedges. In that case, each of the structured regions includes at least one wedge or partial wedge from two different sets of wedges or partial wedges.

  Wedges or partial wedges from different sets of wedges or partial wedges have different refractive indices.

  Such a structured membrane or plate can be obtained, for example, by the following method. Wedges having an angle α may be formed on glass substrates using photolithography and etching techniques, and a plastic or glass material is applied and molded over these wedges. Another way to prepare this type of structured film or plate is to apply a photocurable resin to the substrate with wedges and polymerize the resin in the preferred mold. The first wedge may be realized using a plastic material instead of being formed by glass etching. Here, the case where the transparent substrate and the first set of wedges have the same refractive index will be described for simplicity.

In this third aspect of the invention, which differs from the first and second aspects, the most intense ambient light, eg sunlight, enters the display from a direction perpendicular to the display surface. The front side surfaces of the individual structured parts (wedges) of the structured film 310 can be set at a Brewster angle θ _{B with} respect to the display surface. The incident light is split into two rays, one having linear polarization with an electrical vector oscillating parallel to the entrance plane (306) and one having an electrical vector oscillating perpendicular to the entrance plane 306 (307). A portion of incident light having linearly polarized light having an electric vector oscillating parallel to the entrance surface 306 passes through the film having a structure having one or more Brewster angles without any reflection. The light is refracted at the interface between the film 310 having a structure having one or more Brewster angles and the wedge having the angle α 309, passes through the transparent substrate 301, and reaches the polarizer 302. Here, the transmission axis of the polarizer 302 can be set parallel to the vibration direction of the polarized light 306, and thus the polarized light 306 does not pass through the polarizer 302.

  Other polarized light having an electric vector that oscillates perpendicular to the entrance surface 307 splits into reflective and transmissive portions at the interface between the air and the film 310 having a structure having one or more Brewster angles. . The reflector goes in the direction of the side of the display and does not reach the cholesteric liquid crystal layer 304 and will probably be ignored. The transmission part is refracted like the polarized light 306 and reaches the polarizer 302. The polarized light 307 passes through the polarizer 302 and reaches selective reflection. However, it is possible to design the display so that practically acceptable contrast is maintained. This is accomplished as follows.

  Initially, some of the polarized light 307 is reflected and the intensity of the transmitted light is reduced compared to not using a film having a structure with one or more Brewster angles. The greater the refractive index n of the film having a structure having one or more Brewster angles used, the lower the intensity of the transmitted light and thus the higher the contrast obtained. The polarized light 307 is refracted at the interface between media having different refractive indexes and enters the cholesteric liquid crystal layer from an oblique direction. By controlling the angle of incidence of the polarized light 307 on the cholesteric liquid crystal layer, and controlling the refractive index n ′ of the wedge 309 and their angle α, the wavelength range of selective reflection is longer, and thus more important in the spectrum. Can be moved to a non-existing region, and the direction of the reflected light from the direction of propagation of the emitted polarized light 308 can be moved, thus maintaining a practically acceptable contrast and good quality display. It is possible to obtain

  Furthermore, the light scattering film 305 acting as an enhancement film can be omitted. When the film 305 is removed, the viewing angle is narrowed, but only the emitted light can be observed from a typical direction, in which case the contrast is very high.

  Assuming that the transparent substrate 301 is made of glass with a refractive index of 1.45 and the wedges with an angle α have the same refractive index of 1.45, β of a film having a structure with one or more Brewster angles. 4 (angle between the normal to the display surface and polarized light having an electric vector oscillating perpendicular to the entrance surface 307, ie p-polarized light) as a function of the angle α for different values of the refractive index n. Shown in For obvious practical reasons, the value of the angle α should not be greater than 90 °.

  Similarly, in FIG. 5, the change in γ of a film having a structure having one or two or more Brewster angles, that is, a vertical line with respect to the display surface (that is, a vertical line with respect to the light scattering film) and light emission from the cholesteric liquid crystal layer The angle with respect to the polarized light is shown as a function of the angle α for different values of the refractive index n.

  4 and 5 show that when the refractive index n of a film having a structure having one or more Brewster angles is too small, light emitted from the cholesteric liquid crystal layer cannot be observed. When the refractive index of a film having a structure having one or more Brewster angles is 2.0, the value of α is 82 °, β is equal to 6.1 °, and γ is −3.2. Equal to °. In this case, the light reflected by the cholesteric liquid crystal layer 304 having the reflection angle β (6.1 °) reenters the transparent substrate 301 and the film 310 having the Brewster angle, but the reflected light is reflected between the film 310 and the air. Is totally reflected at the interface between the two and the reflected light is not observed. Thus, a significantly increased contrast can be achieved. When the light scattering film 305 for increasing the viewing angle is omitted, the viewing angle becomes narrower. However, when the display is viewed from an angle of 3.2 ° called the “tilt angle”, very high contrast is obtained because no light is reflected from the cholesteric liquid crystal layer. Even if the light reflected by the cholesteric liquid crystal layer is observed, when the light scattering film is removed, the optical path is different for the reflected light and the light emitted from the cholesteric liquid crystal layer 308. Therefore, the display may be viewed from a direction in which only emitted light is observed and high contrast is obtained. When using a light scattering film, a sufficiently high contrast is obtained because the intensity of the light reflected by the cholesteric liquid crystal layer has already been reduced.

  In a fourth preferred embodiment of the present invention, instead of a film having a structure having one or more Brewster angles, a liquid crystal layer is used to suppress selective reflection from the cholesteric liquid crystal layer. A liquid crystal layer having a vertical alignment is most suitable for this particular embodiment.

  FIG. 6 shows a cross section of a fourth preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal layer having a vertical alignment. A liquid crystal 601 is sandwiched between a set of transparent electrodes and an alignment layer on a substrate, both of which are not shown in FIG. 6, and its director is aligned perpendicular to the display surface. In this case, the liquid crystal preferably has negative dielectric anisotropy.

  The quarter-wave plate 602 and the polarizer 603 in the wide wavelength range are adjusted so that only circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 605 passes through them. For example, the most intense ambient light, such as sunlight, enters the display from a direction perpendicular to the display surface. On the other hand, circularly polarized incident light having the same rotation direction as the twist direction of the cholesteric liquid crystal layer 606 cannot pass through the combination of the polarizer 603 and the quarter wave plate 602 and does not reach the cholesteric liquid crystal layer. On the other hand, circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 607 passes through the polarizer 603 and the quarter-wave plate 602. When no electric field is applied to the liquid crystal layer, the circularly polarized light 607 reaches the cholesteric liquid crystal layer without changing the rotation direction. Since the circularly polarized light 607 has a rotational direction opposite to the twist direction of the cholesteric liquid crystal layer 605, it passes through it without interacting with the cholesteric liquid crystal layer. Therefore, selective reflection does not occur and therefore the contrast is not reduced. If necessary and / or desired, a light absorbing layer can be used behind the cholesteric liquid crystal layer. In that case, a light source that excites a light emitting portion present in the cholesteric liquid crystal may be disposed on a side surface of the cholesteric liquid crystal layer 605.

  For example, for large displays, the pixels of the liquid crystal layer and the light-emitting cholesteric liquid crystal layer used for signage can be easily aligned and driven separately, the light emission from the cholesteric liquid crystal layer can be It can be switched off for the pixel. Here, it is possible to separate the light emitting layer and the switching layer and to orient them to match each pixel. In this case, the switching liquid crystal layer can be driven separately from the light emitting cholesteric liquid crystal layer. The latter can be activated by electrical excitation as the OLED itself or by excitation from an external light source such as an LED, OLED or fluorescent lamp.

  However, the cholesteric liquid crystal layer shines over the entire display area, for example for small pixel displays, such as those where separation of the emissive and switching layers is not possible and color filters must typically be used for color display. Even in this case, the improvement of the present invention will be achieved. Here, the circularly polarized light emitted from the cholesteric liquid crystal layer 608 is increased circularly polarized light having circular polarization in the same direction as the twisted direction of the cholesteric liquid crystal layer mainly due to a resonance effect. A combination of a quarter wave plate and a polarizer can be used to convert the emitted light to pure circular polarization. Circularly polarized light from the cholesteric liquid crystal layer passes through the liquid crystal layer 601 without any interaction and reaches the quarter-wave plate 602 and the polarizer 603. It cannot pass through the combination of quarter wave plate 602 and polarizer 603, thus resulting in a completely black pixel.

  When the display is switched on, an electric field is applied to the liquid crystal layer 601 to induce optical retardation in the liquid crystal layer 601 while light is activated by activating the cholesteric liquid crystal layer itself as an OLED or by excitation by external light, Light is emitted from the cholesteric liquid crystal layer. When the induced phase difference is equal to π, the liquid crystal layer 601 acts as a half-wave plate. Circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 607 changes its rotation direction through the liquid crystal layer 601 and changes to circularly polarized light having the same rotation direction as the twist direction of the cholesteric liquid crystal layer. This circularly polarized light having the same rotational direction as the twisted direction of the cholesteric liquid crystal layer is reflected by the cholesteric liquid crystal layer 605 without changing the rotational direction, and enters the liquid crystal layer 601 again. Through the liquid crystal layer 601, it changes its rotational direction again and becomes circularly polarized light having a rotational direction opposite to the twist direction of the cholesteric liquid crystal layer that can pass through the quarter wave plate 602 and the polarizer 603.

  Circularly polarized light emitted from the cholesteric liquid crystal layer 608 also changes its rotational direction through the liquid crystal layer 601 and passes through the combination of the quarter wave plate 602 and the polarizer 603. Thus, in this preferred embodiment of the present invention, the ambient light that reaches the cholesteric liquid crystal and is reflected by the cholesteric liquid crystal layer 605 and the light emitted from the cholesteric liquid crystal layer 608 both have the same light interaction as the liquid crystal layer 601. Thus, selective reflection of ambient light does not reduce contrast, but rather increases display brightness and increases contrast.

  This preferred embodiment of the invention in principle does not require the use of color filters. However, it is possible to use color filters to improve color purity and eliminate possible orientation problems (parallax) of displays with small pixels. In this preferred embodiment of the present invention, the liquid crystal layer 601 may operate as a switching element, which has only the basic function of switching on and off, and the brightness may be controlled by the intensity of light emitted from the cholesteric liquid crystal layer 605, Alternatively, the cholesteric liquid crystal layer may operate as a backlight that is always on, and the brightness is controlled by the liquid crystal layer 601 as in a conventional liquid crystal device. In the latter case, the brighter the ambient light, the stronger the selective reflection, so it would be desirable to have a monitoring system for ambient light that controls the radiant intensity of the cholesteric liquid crystal layer. Especially in the latter case, this preferred embodiment of the present invention has unique features and is quite different from ordinary liquid crystal display devices.

  In this preferred embodiment of the present invention, the light scattering film 604 is preferably used to increase the viewing angle to obtain a wide field of view.

  The liquid crystal layer 601 must change its phase difference only between 0 and π. Thus, according to this preferred aspect of the present invention, a fairly large value of Δn · d (where d is the thickness of the liquid crystal layer and Δn is a value that cannot be used in conventional vertical alignment mode liquid crystal display devices). It is possible to use a liquid crystal layer 601 (which is optical anisotropy of liquid crystal). This is because an excessively large value of Δn · d will result in unacceptably narrow viewing angle features. A liquid crystal layer with a large value of Δn · d has the advantage of a very fast response since even a slight change in the director angle induces a sufficiently large retardation change for switching.

  In conventional vertical alignment mode liquid crystal display devices, it is proposed to divide each pixel into four degenerate domains in order to obtain a wide field of view. In each of these four degenerate regions, the liquid crystal director is tilted toward the substrate in one of four different directions, one in each of the four quadrants. This requires additional processing, such as building protrusions for each pixel, patterning the transparent electrode or providing different surface treatments for different areas. However, each of these processes causes higher manufacturing costs.

  However, this preferred aspect of the present invention does not require any such additional processing. This is because circularly polarized light enters the liquid crystal layer 601 and therefore the liquid crystal must change only its retardation regardless of which direction the liquid crystal director is tilted. Furthermore, in the conventional liquid crystal display device using the vertical alignment mode, the aperture ratio is reduced because light is not transmitted in the direction of the transmission axis of the polarizer and the direction perpendicular thereto. In this preferred embodiment of the present invention, since circularly polarized light enters the liquid crystal layer 601, the aperture ratio is reduced and a bright image is obtained regardless of whether the pixel is divided into a plurality of regions.

  The light emitted from the cholesteric liquid crystal layer 605 has a relatively small spread, that is, it is distributed only over a narrow range of angles that develop around the normal to the plane of the layer, so that selective reflection is suppressed and high contrast is achieved. The gap between the cholesteric liquid crystal layer 605 and the liquid crystal layer 601 that realizes the ratio may be thin. However, a larger gap is generally preferred considering the angular dependence of selective reflection. In particular, when using a color filter, it is desirable to make the gap as thick as possible. However, there are practical and theoretical limits on the gap thickness. In particular, in order to suppress any parallax, a gap thickness of 1.0 mm or less, more preferably 750 μm or less, and most preferably 430 μm or less is preferable.

The wavelength of the selective reflection matches that of light emitted from the cholesteric liquid crystal layer 608 for normal incidence. When the incident angle deviates from 0 °, the change in selective reflection wavelength (Δλ) is proportional to the original wavelength (λ) of selective reflection and is sin (Δθ) × Δθ, where Δθ is a cholesteric liquid crystal The angle of incidence on the layer. The 10% selective reflection wavelength shift from the original wavelength of selective reflection is when the square value of Δθ (ie (Δθ) ² ) is approximately 0.1 (ie (Δθ) ² = 0.1). To occur. This results in Δθ = 0.32 (arcs, rad) corresponding to about 20 °.

  Therefore, it is desirable to prevent ambient light having an incident angle greater than 20 ° from reaching the cholesteric liquid crystal layer 605. For example, assuming a pixel width of 100 μm, each pixel is preferably surrounded by a “wall” with a height of approximately 137 μm (obtained from 100 μm / (2 × tan (20 °)) = 137 μm), At the same time it should be as thin as possible in the lateral direction. Further, a microlens array that converges ambient light and adjusts the incident angle of light to the cholesteric liquid crystal layer 605 to a value within a range of ± 20 ° is inserted between the light scattering film 604 and the liquid crystal layer 601. In this case, the light scattering film 604 is optional and may be removed.

  In this embodiment, an optical element composed of a polarizer sandwiched between two wide wavelength band quarter-wave plates can be applied to complete circular polarization of circularly polarized light from a cholesteric liquid crystal layer.

  In the fifth preferred embodiment of the present invention, the liquid crystal layer is selectively reflected from the cholesteric liquid crystal layer in place of the film having a structure having one or more Brewster angles as in the fourth embodiment. Used to suppress. However, the liquid crystal layer in this fifth preferred embodiment of the invention is a twisted nematic liquid crystal layer. In this case, the liquid crystal has positive dielectric anisotropy.

  FIG. 7 shows a cross section of a fifth preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal layer that is a twisted nematic liquid crystal layer. The liquid crystal 701 is sandwiched between a pair of transparent electrodes and an alignment layer on the substrate, both of which are not shown in FIG. Typically, the surfaces of two substrates facing each other are aligned for homogeneous alignment of the liquid crystal, ie, alignment of the director of the liquid crystal parallel to the display surface. The alignment layer for homogeneous alignment is subjected to alignment treatment such as rubbing for introducing alignment in one preferred direction. For twisted nematic orientation, the two substrates are assembled to form cells with their respective directions of preferred orientation rotating relative to each other.

  Thus, the orientation of the director of the liquid crystal twists transversely from one substrate to another through the cell over several predetermined angles. This torsion angle is usually set to 90 °, but in the range from 70 ° to 90 °, or in particular to improve the dependence of the intensity of the reflected light from the cell gap, it is greater than 90 °, for example 90 °. It can also be in the range from ° to 110 °. However, the torsion angle can also be set close to or at 0 °.

  Here, as in the fourth preferred embodiment of the present invention, the quarter-wave plate 702 and the polarizer 703 in the wide wavelength range are changed so that only circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 705 is obtained. Adjust to get through them. For example, the most intense ambient light, such as sunlight, enters the display from a direction perpendicular to the display surface. On the other hand, circularly polarized incident light having the same rotation direction as the twist direction of the cholesteric liquid crystal layer 706 cannot pass through the combination of the polarizer 703 and the quarter wave plate 702 and does not reach the cholesteric liquid crystal layer. On the other hand, circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 707 passes through the polarizer 703 and the quarter-wave plate 702. When no electric field is applied to the liquid crystal layer, the circularly polarized light 707 reaches the cholesteric liquid crystal layer without changing the rotation direction. Since the circularly polarized light 707 has a rotational direction opposite to the twist direction of the cholesteric liquid crystal layer 705, it passes through it without interacting with the cholesteric liquid crystal layer. Therefore, selective reflection does not occur, and thus the contrast is not reduced. If necessary and / or desired, a light absorbing layer can be used behind the cholesteric liquid crystal layer. In this case, a light source that excites a light emitting portion present in the cholesteric liquid crystal may be disposed on the side surface of the cholesteric liquid crystal layer 705.

  For example, for large displays, the pixels of the liquid crystal layer and the light-emitting cholesteric liquid crystal layer used for signage can be easily aligned and driven separately, the light emission from the cholesteric liquid crystal layer can be It can be switched off for the pixel. Here, it is possible to separate the light emitting layer and the switching layer and to orient them to match each pixel. In this case, the switching liquid crystal layer can be driven separately from the light emitting cholesteric liquid crystal layer. The latter can be activated by electrical excitation as the OLED itself or by excitation from an external light source such as an LED, OLED or fluorescent lamp.

  However, the cholesteric liquid crystal layer shines over the entire display area, for example for small pixel displays, such as those where separation of the emissive and switching layers is not possible and color filters must typically be used for color display. Even in this case, the improvement of the present invention will be achieved. Here, the circularly polarized light emitted from the cholesteric liquid crystal layer 708 is increased circularly polarized light having circular polarization in the same direction as the twisted direction of the cholesteric liquid crystal layer mainly due to a resonance effect. A combination of a quarter wave plate and a polarizer can be used to convert the emitted light to pure circular polarization. Circularly polarized light from the cholesteric liquid crystal layer passes through the liquid crystal layer 701 without any interaction and reaches the quarter-wave plate 702 and the polarizer 703. It cannot pass through the combination of quarter wave plate 702 and polarizer 703, thus resulting in a completely black pixel.

  When the display is switched on, an electric field is applied to the liquid crystal layer 701 to induce optical retardation in the liquid crystal layer 701 while operating the cholesteric liquid crystal layer itself as an OLED or by excitation with external light. Emit light. When the induced phase difference is equal to π, the liquid crystal layer 701 acts as a half-wave plate. Circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 707 changes its rotation direction through the liquid crystal layer 701 and changes to circularly polarized light having the same rotation direction as the twist direction of the cholesteric liquid crystal layer. This circularly polarized light having the same rotational direction as the twisted direction of the cholesteric liquid crystal layer is reflected by the cholesteric liquid crystal layer 705 without changing the rotational direction, and enters the liquid crystal layer 701 again. Through the liquid crystal layer 701, it changes its rotational direction again and becomes circularly polarized light having a rotational direction opposite to the twist direction of the cholesteric liquid crystal layer that can pass through the quarter wave plate 702 and the polarizer 703.

  Circularly polarized light emitted from the cholesteric liquid crystal layer 708 also changes its rotational direction through the liquid crystal layer 701 and passes through the combination of the quarter wave plate 702 and the polarizer 703. Thus, in this preferred embodiment of the invention, the ambient light that reaches the cholesteric liquid crystal and is reflected by the cholesteric liquid crystal layer 705 and the light emitted from the cholesteric liquid crystal layer 708 both have the same light interaction as the liquid crystal layer 701. Thus, selective reflection of ambient light does not reduce contrast, but rather increases display brightness and increases contrast.

  This preferred embodiment of the invention in principle does not require the use of color filters. However, it is possible to use color filters to improve color purity and eliminate possible orientation problems (parallax) of displays with small pixels. In this preferred embodiment of the present invention, the liquid crystal layer 701 may operate as a switching element, which has only the basic function of turning on and off, and the brightness may be controlled by the intensity of light emitted from the cholesteric liquid crystal layer 705, Alternatively, the cholesteric liquid crystal layer may operate as a backlight that is always on, and the brightness is controlled by the liquid crystal layer 701 as in a conventional liquid crystal device. In the latter case, it would be desirable to provide a monitoring system for ambient light that controls the radiant intensity of the cholesteric liquid crystal layer, so that the brighter the ambient light, the stronger the selective reflection. Especially in the latter case, this preferred embodiment of the present invention has unique features and is quite different from ordinary liquid crystal display devices.

  In this preferred embodiment of the present invention, the light scattering film 704 is preferably used to increase the viewing angle to obtain a wide field of view.

  The liquid crystal layer 701 has to change its phase difference only between 0 and π. Thus, according to this preferred embodiment of the present invention, a fairly large value of Δn · d (where d is the thickness of the liquid crystal layer and Δn is the thickness of the liquid crystal) having values that cannot be used in conventional TN liquid crystal display devices. It is possible to use a liquid crystal layer 701 having optical anisotropy. This is because an excessively large value of Δn · d will result in unacceptably narrow viewing angle features. A liquid crystal layer with a large value of Δn · d has the advantage of a very fast response since even a slight change in the director angle induces a sufficiently large retardation change for switching.

  In conventional TN mode liquid crystal display devices, the orientation direction of the LC director on at least one substrate should be precisely adjusted and in most cases coincides with the transmission axis of the adjacent polarizer. However, in this preferred embodiment of the invention, since the switching element is operated using circularly polarized light, precise control of the direction of orientation of one or more polarizers is not necessary. Therefore, the orientation direction of the polarizer on the substrate can be arbitrarily selected. This results in improved yields in manufacturing.

  The light emitted from the cholesteric liquid crystal layer 705 has a relatively small spread, that is, it is distributed over only a narrow range of angles that develop around the normal to the plane of the layer, so that selective reflection is suppressed and high contrast is achieved. The gap between the cholesteric liquid crystal layer 705 and the liquid crystal layer 701 that realizes the ratio may be thin. However, a larger gap is generally preferred considering the angular dependence of selective reflection. In particular, when using a color filter, it is desirable to make the gap as thick as possible. However, there are practical and theoretical limits on the gap thickness. In particular, in order to suppress any parallax, a gap thickness of 1.0 mm or less, more preferably 750 μm or less, and most preferably 430 μm or less is preferable.

The wavelength of the selective reflection matches that of light emitted from the cholesteric liquid crystal layer 708 for normal incidence. When the incident angle deviates from 0 °, the change in selective reflection wavelength (Δλ) is proportional to the original wavelength (λ) of selective reflection and is sin (Δθ) × Δθ, where Δθ is a cholesteric liquid crystal The angle of incidence on the layer. The 10% selective reflection wavelength shift from the original wavelength of selective reflection is when the square value of Δθ (ie (Δθ) ² ) is approximately 0.1 (ie (Δθ) ² = 0.1). To occur. This results in Δθ = 0.32 (arcs, rad) corresponding to about 20 °.

  Therefore, it is desirable to prevent ambient light having an incident angle greater than 20 ° from reaching the cholesteric liquid crystal layer 705. For example, assuming a pixel width of 100 μm, each pixel is preferably surrounded by a “wall” with a height of approximately 137 μm (obtained from 100 μm / (2 × tan (20 °)) = 137 μm), At the same time it should be as thin as possible in the lateral direction. Further, a microlens array that converges ambient light and adjusts the incident angle of light to the cholesteric liquid crystal layer 705 to a value within a range of ± 20 ° is inserted between the light scattering film 704 and the liquid crystal layer 701. In this case, the light scattering film 704 is optional and may be removed.

  In this embodiment, an optical element composed of a polarizer sandwiched between two wide wavelength band quarter-wave plates can be applied to complete circular polarization of circularly polarized light from a cholesteric liquid crystal layer.

  FIG. 8 shows a cross section of a sixth preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal layer having a hybrid alignment nematic liquid crystal. The liquid crystal 801 is sandwiched between a pair of transparent electrodes and an alignment layer on each substrate, both of which are not shown in FIG.

  In a sixth preferred embodiment of the invention, different substrates are oriented for different orientations for hybrid orientation. Typically, the surface of one substrate is oriented for homogeneous alignment of the liquid crystal, i.e., alignment of the director of the liquid crystal parallel to the display surface, while the surface of the other substrate is homeotropically aligned, That is, the alignment treatment is performed for alignment of the director of the liquid crystal perpendicular to the display surface. Therefore, the orientation of the director of the liquid crystal is tilted vertically over some angle from one substrate to the paired substrate. The inclination angle is normally set to 90 °, but may be in a range from 70 ° to 90 °.

  On the one hand, in this preferred embodiment of the present invention, similar to the fifth preferred embodiment of the present invention, when the liquid crystal layer 801 operates in a normally white mode, a higher contrast is achieved by the surface alignment treatment. On the other hand, when it is operated in a normally black mode, high contrast is achieved without any surface treatment for orientation, in which case the aperture ratio is slightly reduced.

  When the liquid crystal layer 801 operates in a normally white mode, the polarizer 803 and the quarter wave plate 802 are adjusted so that only circularly polarized light having a rotation direction opposite to the twist direction of the cholesteric liquid crystal layer 705 passes through them. To do. The Δn · d value of the liquid crystal layer 801 having a hybrid alignment nematic (HAN) mode is adjusted so that the liquid crystal layer 801 functions as a half-wave plate. By changing the cell thickness of the liquid crystal layer 801, it is possible to adjust the retardation of the liquid crystal layer 801 for the three primary colors, R, G and B, for each cell corresponding to the color of the cholesteric liquid crystal layer 805. Yes, or alternatively, it may be adjusted for one representative color, for example green, where the human eye has the highest sensitivity.

  As shown in the lower half of FIG. 8, the circularly polarized light passing through the polarizer 803 and the quarter-wave plate 802 changes its rotational direction through the liquid crystal layer and has the same rotational direction as the twist direction of the cholesteric liquid crystal layer 805. It reaches the cholesteric liquid crystal layer 805 as circularly polarized light. This circularly polarized light is reflected by the cholesteric liquid crystal layer 805, changes its rotational direction again through the liquid crystal layer 801, and passes through the quarter-wave plate 802 and the polarizer 803. Circularly polarized light 808 emitted from the cholesteric liquid crystal layer 805 also changes its rotational direction through the liquid crystal layer and passes through the quarter-wave plate 802 and the polarizer 803.

  As shown in the upper half of FIG. 8, when an electric field is applied to the liquid crystal layer 801, the director of the liquid crystal is aligned perpendicular to the substrate surface, and its retardation almost disappears (ie, close to 0 or becomes 0). At this time, the circularly polarizing layer having a rotation opposite to the twist direction of the cholesteric liquid crystal 805 passes through the polarizer 803 and the quarter-wave plate 802 and reaches the cholesteric liquid crystal layer without changing the rotation direction. Not reflected. The circularly polarized light 808 emitted from the cholesteric liquid crystal layer 805 cannot pass through the polarizer 803.

  Accordingly, the display operates in a normally white mode with respect to the liquid crystal layer 801. In this case, it is desirable to use an alignment treatment for the alignment layer in order to avoid the occurrence of disclination lines. However, accurate alignment of the liquid crystal director on the substrate having the transmission axis of the polarizer 803 is not necessary. On the other hand, when the liquid crystal layer 801 operates in the normally black mode, regardless of the change of the liquid crystal layer 801, the disclination line does not change the retardation and remains black, and thus no deterioration in contrast occurs. Similar to the fifth preferred embodiment of the present invention, the entire area of the disclination line is small and the aperture ratio is hardly reduced.

  When the liquid crystal layer 801 operates in a normally black mode, the polarizer 803 and the quarter wave plate 802 are set so that they transmit circularly polarized light having the same rotational direction as the twist direction of the cholesteric liquid crystal layer 805. .

  Here, similar to the fourth and fifth preferred embodiments of the present invention, a color filter can be attached, and a feedback system for ambient light for controlling the intensity of light emitted from the cholesteric liquid crystal layer is desirable. .

  The light emitted from the cholesteric liquid crystal layer 805 has a relatively small spread, that is, it is distributed only over a narrow range of angles that develop around the normal to the plane of the layer, so that selective reflection is suppressed and high contrast is achieved. The gap between the cholesteric liquid crystal layer 805 and the liquid crystal layer 801 that realizes the ratio may be thin. However, a larger gap is generally preferred considering the angular dependence of selective reflection. In particular, when using a color filter, it is desirable to make the gap as thick as possible. However, there are practical and theoretical limits on the gap thickness. In particular, in order to suppress any parallax, a gap thickness of 1.0 mm or less, more preferably 750 μm or less, and most preferably 430 μm or less is preferable.

The wavelength of the selective reflection matches that of light emitted from the cholesteric liquid crystal layer 808 for normal incidence. When the incident angle deviates from 0 °, the change in selective reflection wavelength (Δλ) is proportional to the original wavelength (λ) of selective reflection and is sin (Δθ) × Δθ, where Δθ is a cholesteric liquid crystal The angle of incidence on the layer. The 10% selective reflection wavelength shift from the original wavelength of selective reflection is when the square value of Δθ (ie (Δθ) ² ) is approximately 0.1 (ie (Δθ) ² = 0.1). To occur. This results in Δθ = 0.32 (arcs, rad) corresponding to about 20 °.

  Therefore, it is desirable to prevent ambient light having an incident angle greater than 20 ° from reaching the cholesteric liquid crystal layer 805. For example, assuming a pixel width of 100 μm, each pixel is preferably surrounded by a “wall” with a height of approximately 137 μm (obtained from 100 μm / (2 × tan (20 °)) = 137 μm), At the same time it should be as thin as possible in the lateral direction. Furthermore, a microlens array that converges ambient light and adjusts the incident angle of light to the cholesteric liquid crystal layer 805 to a value within a range of ± 20 ° is inserted between the light scattering film 804 and the liquid crystal layer 801. In this case, the light scattering film 804 is optional and may be removed.

  As shown in FIG. 9 for the seventh preferred embodiment of the present invention, a bend alignment mode liquid crystal layer may be beneficially used to suppress selective reflection in the same manner as described above. Bend alignment is achieved by aligning the liquid crystal, for example by rubbing, by surface treating the substrate for antiparallel alignment. When an electric field is applied to the liquid crystal layer 901, the initial splay alignment is changed to bend alignment. This mode has an advantage that the response speed of the liquid crystal layer 901 is particularly fast. Even when the liquid crystal layer 901 is operated in the normally white mode, the occurrence of a disclination line that deteriorates the contrast will be avoided by applying the alignment treatment. This preferred embodiment of the invention using the liquid crystal layer in bend mode also has the advantage that it does not require precise alignment of the orientation of the liquid crystal at the substrate surface relative to the transmission axis of the respective polarizer.

  FIG. 10 shows a cross section of an eighth preferred embodiment of the present invention in which selective reflection of a cholesteric liquid crystal layer is suppressed using an in-prene switching (IPS) type liquid crystal layer. This description applies to a conventional IPS liquid crystal mode in which the electrodes are located only on the substrate on one side of the liquid crystal layer. This type of electrode is also called an interdigital electrode.

  Here, the liquid crystal is preferably in a nematic phase and has either positive or negative dielectric anisotropy, but positive dielectric anisotropy is preferred. In this embodiment, the electrodes are formed on one substrate, and the liquid crystal 1001 is driven by an electric field perpendicular to the substrate and by an electric field that is parallel to the substrate. However, the most efficient is the non-uniform component of the electric field. The liquid crystal layer may also be driven by a transient electric field, ie an electric field that does not exist permanently. This mode is also referred to as a fringe field switching (FFS) mode. Although two electrodes are depicted as one layer in FIG. 10, they may exist in different layers sandwiching the insulating layer. The electrode may be made of either transparent, conductive material or metal. In particular, when two electrodes sandwich an insulator, the electrode close to the substrate is preferably made of a transparent material and preferably covers the entire area of the pixel.

  In this preferred embodiment, ie the eighth preferred embodiment of the present invention, an alignment layer is preferably formed on both substrates and the director of the liquid crystal 1001 is homogeneously aligned with an alignment layer having only a small surface tilt angle. Alignment treatment. The orientations of the directors of the liquid crystal on the two substrates are parallel to each other or form different angles. Preferably it is parallel.

In an alternative realization of this preferred embodiment of the invention, a ferroelectric liquid crystal is used instead of a nematic liquid crystal. Surface ferroelectric liquid crystal stabilization mode (SSFLC) are preferably used both a chiral smectic liquid crystal of S _C ^* phase sandwiched between two substrates having electrodes and an alignment layer on the inner surface thereof To do. With this shape, the liquid crystal director also switches in the face of the switching element, as in a conventional TN element.

  In this preferred embodiment of the present invention, when the liquid crystal layer 1001 operates in a normally black mode, higher contrast due to the smaller effect of chromatic dispersion of the liquid crystal layer 1001 compared to operating in a normally white mode. Is achieved. Polarizers 1003 and 1006 are arranged on both sides of the liquid crystal layer 1001 so that their transmission axes are perpendicular to each other, and a quarter-wave plate 1002 in the wide wavelength range has the same rotational direction as the twist direction of the cholesteric liquid crystal layer. The circularly polarized light is disposed between the polarizer 1003 and the cholesteric liquid crystal layer 1005 so as to pass through the polarizer 1003 and the quarter-wave plate 1002. The director of the liquid crystal layer 1001 on the substrate preferably coincides with the transmission axis of one of the two polarizers 1003 or 1006. In FIG. 10, the case where it corresponds with the polarizer 1006 located in the observer side is illustrated.

  On the other hand, in the lower half of FIG. 10, when no electric field is applied to the liquid crystal layer 1001, ambient light passing through the polarizer 1006 passes through the liquid crystal layer 1001 without changing its polarization state, and reaches the polarizer 1003. However, it cannot pass through this polarizer 1003. Circularly polarized light 1008 emitted from the cholesteric liquid crystal layer 1005 is converted into linearly polarized light by the quarter-wave plate 1002, and passes through the polarizer 1003 as linearly polarized light, and moves through the liquid crystal layer 1001 without changing its polarization state. , Blocked by a polarizer 1006.

  On the other hand, as shown in the upper half of FIG. 10, when the electric field having a substantially horizontal component (that is, the lateral direction with respect to the surface of the switching element) is applied, the liquid crystal layer 1001 is a half-wave plate when the electric field is applied. When applied to a liquid crystal layer 1001 having a Δn · d value adjusted to induce π retardation, the ambient light 1007 passing through the polarizer 1006 passes through the liquid crystal layer 1001 and its polarization state. And pass through the polarizer 1003 and the quarter-wave plate 1002. The polarization state is circularly polarized light having the same rotation direction as the twist direction of the cholesteric liquid crystal layer 1005. Accordingly, the cholesteric liquid crystal layer 1005 reflects ambient light traveling in the same optical path in the reverse direction. This light first passes through the liquid crystal layer 1001 and again through the polarizer 1006. Circularly polarized light 1008 emitted from the cholesteric liquid crystal layer 1005 also travels along the same optical path and passes through the polarizer 1006. Both rays may be observed directly or through an optional light scattering film 1004 that may be applied to increase the viewing field (ie viewing angle) if necessary.

  Accordingly, the display operates in a normally black mode with respect to the liquid crystal layer 1001, as in the fourth, fifth and sixth preferred embodiments of the present invention. When the display is in the black state, ambient light selective reflection does not occur in the cholesteric liquid crystal layer 1005, and ambient light selective reflection occurs only when the display is in the white state. This results in an increase in light intensity for the white state and thus an increase in contrast.

  In this preferred embodiment of the present invention, the light scattering film 1004 preferably increases the viewing angle and provides a wide field of view.

  The liquid crystal layer 1001 must only act as a switchable half-wave plate, i.e. only change its retardation from 0 to π. A large Δn · d value can be used for the liquid crystal layer 1001. Therefore, even a small change in director orientation results in a large change in retardation. In other words, they operate with a lower voltage for the liquid crystal layer, resulting in improved switching elements and improved switching element response time (ie, faster response).

  A normally white mode for the liquid crystal layer 1001 can be easily obtained by setting the transmission axes of the polarizers 1006 and 1003 parallel to each other. In this case, similarly to the normally black mode, selective reflection from the cholesteric liquid crystal layer 1005 can be suppressed, and a switching element having a high contrast ratio can be realized.

  The light emitted from the cholesteric liquid crystal layer 1005 has a relatively small spread, that is, it is distributed only over a narrow range of angles that develop around the normal to the plane of the layer, so that selective reflection is suppressed and high contrast is achieved. The gap between the cholesteric liquid crystal layer 1005 and the liquid crystal layer 1001 that realizes the ratio may be thin. However, a larger gap is generally preferred considering the angular dependence of selective reflection. In particular, when using a color filter, it is desirable to make the gap as thick as possible. However, there are practical and theoretical limits on the gap thickness. In particular, in order to suppress any parallax, a gap thickness of 1.0 mm or less, more preferably 750 μm or less, and most preferably 430 μm or less is preferable.

The wavelength of the selective reflection matches that of light emitted from the cholesteric liquid crystal layer 1008 for normal incidence. When the incident angle deviates from 0 °, the change in selective reflection wavelength (Δλ) is proportional to the original wavelength (λ) of selective reflection and is sin (Δθ) × Δθ, where Δθ is a cholesteric liquid crystal The angle of incidence on the layer. The 10% selective reflection wavelength shift from the original wavelength of selective reflection is when the square value of Δθ (ie (Δθ) ² ) is approximately 0.1 (ie (Δθ) ² = 0.1). To occur. This results in Δθ = 0.32 (arcs, rad) corresponding to about 20 °.

  Therefore, it is desirable to prevent ambient light having an incident angle greater than 20 ° from reaching the cholesteric liquid crystal layer 1005. For example, assuming a pixel width of 100 μm, it is desirable that each pixel be surrounded by a “wall” with a height of approximately 137 μm (obtained from 100 μm / (2 × tan (20 °)) = 137 μm). At the same time it should be as thin as possible in the lateral direction. Further, a microlens array that converges ambient light and adjusts the incident angle of light to the cholesteric liquid crystal layer 1005 to a value within a range of ± 20 ° is inserted between the light scattering film 1004 and the liquid crystal layer 1001. In this case, the light scattering film 1004 is optional and may be removed.

  The in-plane switching type nematic liquid crystal layer can be replaced by a conventional TN, VA, hybrid alignment or bend mode liquid crystal cell by aligning the alignment direction of the liquid crystal with the transmission axis of the polarizer.

  However, a more preferred alternative is a ferroelectric liquid crystal layer. To achieve this object, the interdigital electrode shown in FIG. 10 is replaced with a set of transparent electrodes sandwiching the liquid crystal layer shown in FIGS. 8 and 9, while maintaining the device structure of FIG. The optical behavior of the resulting switching element is essentially the same as in the in-plane switching nematic liquid crystal layer, for example, the rubbing direction for the ferroelectric liquid crystal layer is on the adjacent side of the cholesteric liquid crystal layer. It should coincide with the transmission axis of the polarizer. The surface stabilized ferroelectric liquid crystal layer has a memory effect and the displayed image is maintained without further electrical addressing. Therefore, this mode is particularly suitable for displays that do not show moving images, such as electronic paper and electric signs, in addition to conventional displays. This also preserves displays consisting of low molecular weight ferroelectric liquid crystals that use a ferroelectric liquid crystal polymer layer instead of a ferroelectric liquid crystal surface stabilizing layer. In the case of a ferroelectric liquid crystal polymer layer, an extension of the polymer film may be used to align the mesogenic component instead of rubbing, and the director of these mesogenic components is preferably on the side of the cholesteric liquid crystal layer It should coincide with the transmission axis of the polarizer.

  The light emission mechanism of the cholesteric liquid crystal layer may be any kind of light emission mechanism, for example, fluorescence by short wavelength light excitation or phosphorescence, or light emission by recombination of holes and electrons injected through the electrode.

  In this preferred embodiment of the present invention, as described with respect to FIG. 6 above, in order to obtain complete circular polarization from the cholesteric liquid crystal layer, there are two wide wavelengths between the cholesteric liquid crystal layer and the optical element that suppresses selective reflection. An optical element including a polarizer sandwiched between quarter-wave plates in the range can also be provided. The optical element can be either a half mirror or a linear polarizer, with at least one quarter wavelength at least on one side, except that the linear polarizer is sandwiched between two wide wavelength range quarter wave plates. It is covered with a plate.

  In order to achieve a high contrast ratio, ambient excitation light is preferably removed outside the cholesteric liquid crystal layer. For this purpose, preferably at least one side of the cholesteric liquid crystal comprising at least one light-emitting moiety is covered directly or indirectly with a layer that absorbs light having a wavelength of 400 nm or less, preferably 470 nm or less. In this specification, “indirectly covering” means that the respective layers are present beside each other. That is, the light absorption layer exists separately from the cholesteric liquid crystal layer, for example, as a protective layer or as a transparent substrate existing between the cholesteric liquid crystal layer and the light absorption layer. This embodiment is particularly useful for a display having an in-cell type luminescent cholesteric liquid crystal layer. In this embodiment, in some cases, a color filter is not necessary. From the outside of the cell, for example, excitation light from an LED, OLED or fluorescent lamp enters the cell from one direction, traverses the cholesteric liquid crystal layer that changes it into circularly polarized light, and before entering the switchable liquid crystal layer Passes through a layer that absorbs light.

  In a preferred embodiment of the invention, the electro-optic switching element comprises two or more means for light emission, preferably three means, preferably one emission of three different wavelengths of primary colors such as red, green and blue. One for each, preferably one of the three layers, one by one, preferably one after the other, preferably in the order of blue, green and red as viewed from the observation side including.

In a further preferred embodiment of the present invention, the electro-optic switching element has three different regions, each having a different emitter, and preferably one emission of three different wavelengths which are primary colors, for example red, green and blue. Each of the three regions preferably has a surface of 90.000 μm ² or less, preferably 450 μm or less, preferably 300 μm or less and most preferably 200 μm or less. .

  If the light scattering film used in any aspect of the invention comprises a polymer dispersed liquid crystal (PDLC) device, the change in viewing angle characteristics can be electrically switched.

  Preferred embodiments of the invention will also be apparent to the expert from the claims of this application and in this respect form part of the disclosure of the present invention.

Examples The following examples are intended to illustrate the invention without any limitation.

  However, the different embodiments, including their composition, composition and physical properties, are very well described for professionals, and the properties can be achieved with the invention in a particularly modifiable range. Thus, in particular, the combination of the various properties that can preferably be achieved is clarified for the expert.

を有する２重量％のキラルドーパント、０．５重量％のAldrichからの蛍光色素「Coumarin 6」および０．２重量％のCiba Speciality Chemicalsからの光開始剤「Irgacure 651」をポリマー前駆物質として混合し、プロピレングリコールモノメチルエーテルアセテート（ＰＧＭＥＡ）に溶解する。溶液の総濃度は５０重量％である。 Example 1a
A cholesteric liquid crystal layer is prepared as follows. Photopolymerizable reactive mesogen “RMM34” from Merck KGaA (93.3% by weight) and the following structure from Merck KGaA

2% by weight chiral dopant, 0.5% by weight fluorescent dye “Coumarin 6” from Aldrich and 0.2% by weight photoinitiator “Irgacure 651” from Ciba Specialty Chemicals as polymer precursors. Dissolve in propylene glycol monomethyl ether acetate (PGMEA). The total concentration of the solution is 50% by weight.

A polyimide alignment layer “SE-7492” in ready-to-apply solution from Nissan Chemical Co., Ltd. is spin-coated on a glass substrate at 1,500 rpm to obtain a film having a thickness of 700 mm. The substrate was pre-baked at 100 ° C. for 3 minutes and cured at 200 ° C. for 1 hour, followed by rubbing in one direction using a cotton cloth. The reactive liquid crystal solution mixed in PMEGA is spin coated at 1,500 rpm on the substrate at the top of the alignment layer, the substrate is baked at 100 ° C. for 20 minutes, and heated to isotropic phase (at about 80 ° C.). Cool the substrate slowly, typically at 1 ° / min, to an ambient temperature of approximately 20 ° C. The cholesteric phase is stabilized by photopolymerization under nitrogen flow by exposure to 2,000 mJ / cm ² 365 nm UV radiation. The resulting chiral pitch is determined at 591 nm using ultraviolet and visible absorption spectra. This cholesteric liquid crystal phase does not change up to 120 ° C. under observation with a polarizing microscope.

The fluorescence intensity from coumarin 6 excited at 365 nm (1 mW / cm ² ) is measured as 25 cd / m ² using a luminance meter CS-1000 (Konica Minolta Holdings, Inc.).

Comparative Example 1
For comparison, another sample is prepared under the same conditions as described in Example 1, but without the chiral dopant in the polymer precursor solution. In that case, the fluorescence intensity is 10 cd / m ² , which is less than half of the value of the sample of Example 1 showing a cholesteric liquid crystal phase.

Example 1b
For confirmation, the following experiment was conducted as to whether selective reflection from the cholesteric liquid crystal sample of Example 1 was suppressed using an optical element having a structure having one or more Brewster angles.

  Commercially available L-circular polarizer (ie, a combination of a polarizer and a quarter wave plate, where the slow axis of the quarter wave plate is rotated 45 ° with respect to the absorption axis of the polarizer) And R-circular polarizer (combination of polarizer and quarter wave plate, where the slow axis of the quarter wave plate is rotated 135 ° with respect to the absorption axis of the polarizer) (both From MeCan Imaging Inc.).

  The substrate on which the cholesteric liquid crystal layer is formed as described above is placed horizontally, and the luminance meter is set to measure the light that enters it vertically from the cholesteric liquid crystal layer. The glass plate is set at an angle of 57 ° with respect to the horizontal plane, and the light from the lamp moves almost horizontally to the glass plate and reflects to the cholesteric liquid crystal layer. Here 57 ° is the Brewster angle of the glass.

The selective reflection intensity is 65.1 cd / m ² when a circular polarizer is not used. When the R-circular polarizer is set so that the transmission axis of the polarizer is perpendicular to the linearly polarized light reflected by the glass surface having a Brewster angle, the selective reflection intensity is reduced to 16.2 cd / m ² . Therefore, the reflected light intensity is reduced to 1/4 or less, and high contrast is obtained. On the other hand, the fluorescence intensity from the cholesteric liquid crystal layer measured for the same sample with and without the R-circular polarizer is reduced only by a ratio of 1 / 1.5, which is much stronger for the use of the R-circular polarizer. Not affected.

Example 2
The polymer precursor solution of Example 1 is spin coated at 1.500 rpm onto a glass substrate covered with the same alignment layer as Example 1 and further processed as described in Example 1. The substrate is baked at 100 ° C. for 20 minutes to remove the solvent. Then, it is cooled to an atmospheric temperature of about 20 ° C., and then heated from the atmospheric temperature to 80 ° C. at which the liquid crystal layer exhibits an isotropic phase (for example, at 3 degrees / minute). Cool the substrate slowly at 1 degree / min. During the cooling process in the temperature range of 70 ° C. to 72 ° C., a blue phase texture is obtained. This texture is also observed at these temperatures in the same processing stage of Example 1. However, in Example 1, the substrate is UV irradiated at ambient temperature where the material is not a blue phase but a chiral nematic phase, so that in this example the blue phase is not immobilized and stabilized.

Compared to Example 1, in this example, ie Example 2, the substrate is not exposed to UV radiation at ambient temperature, ie the temperature at which the material is a chiral nematic phase, and instead a blue phase is observed from 70 ° C. It is carried out in a temperature range of 72 ° C. Otherwise, the sample is exposed to UV irradiation under the same conditions as in Example 1 (exposure at 365 nm, total dose 2,000 mJ / cm ² , exposure under nitrogen flow). Therefore, the blue phase is stable after UV irradiation and the texture does not change between ambient temperature and 120 ° C. It has been shown that the blue phase is stabilized in the form of a film using the reactive mesogenic material RMM34 and UV photopolymerization.

In order to obtain a thicker film of blue phase, which is considered to be a special shape of the cholesteric liquid crystal layer, two substrates covered with an alignment layer, one of which is rubbed in one direction, are formed into a rod-like shape having a diameter of 10 μm. Affix together using a sealant containing spacers. The assembled cell is baked at 150 ° C. for 1 hour to polymerize the sealant. The cell is filled at 80 ° C. with the same polymer precursor mixture as in Example 1, here without solvent. The cell is cooled to a temperature range of 70 ° C. to 72 ° C. and exposed to 365 nm UV radiation for a total of 2,000 mJ / cm ² , while the cell temperature is kept between 70 ° C. and 72 ° C. The blue phase stabilized by this method is used as a luminescent cholesteric liquid crystal layer.

  A liquid crystal cell for vertical alignment mode is prepared using two glass substrates patterned with ITO electrodes on top and covered with a polyimide layer for vertical alignment. The cell gap is 4.9 μm. Fill the cell with liquid crystal material “MLC-2037” from Merck KGaA. This liquid crystal has birefringence (Δn), Δn = 0.0649, and dielectric anisotropy (Δε), Δε = −3.1.

A cell of a cholesteric liquid crystal layer is placed horizontally and irradiated from a direction inclined at an angle of 5 ° with respect to a vertical line with respect to the surface. The intensity of selective reflection from the blue phase cholesteric liquid crystal layer is 654 cd / m ² . By introducing an optical element comprising an L-circular polarizer and a liquid crystal cell for vertical alignment mode between the light source and the cholesteric liquid crystal layer, the intensity of selective reflection is reduced to 44 cd / m ² , It is 1/15 or less of the value, and a high contrast is obtained.

In this measurement, the liquid crystal cell for the vertical alignment mode faces the cholesteric liquid crystal layer, and the light source is very close to the detector of the luminance meter. When only the L-circular polarizer is disposed on the cholesteric liquid crystal layer sample, the intensity of the reflected light is 35 cd / m ² . This is due to the surface reflection of the L-circular polarizer itself and is therefore removed by the anti-reflection coating, and a higher contrast is expected.

By applying a voltage of 5 V to the liquid crystal cell for the vertical alignment mode, a selective reflection intensity of 175 cd / m ² is provided. This indicates that the liquid crystal cell controls the intensity of selective reflection by adjusting the vertical alignment.

Without the optical element for suppressing selective reflection, the fluorescence intensity from the cholesteric liquid crystal layer is 47 cd / m ² . In the optical element that applies 5 V to the liquid crystal cell for the vertical alignment mode, it decreases to 26 cd / m ² . By using this optical element, that is, a combination of an L-circular polarizer and a liquid crystal cell for the vertical alignment mode, the fluorescence intensity is reduced only by 1 / 1.8. Therefore, the effect of the optical element on the light emitted from the cholesteric liquid crystal layer is relatively small.

Example 3
In this example, the sample of the cholesteric liquid crystal layer prepared in Example 1 is used as the light-emitting cholesteric liquid crystal layer.

  The optical element used in Example 2 consisting of an L-circular polarizer and a liquid crystal cell for vertical alignment mode is used here as an optical element for suppressing selective reflection. Similarly, as in Example 2, a sample substrate of a cholesteric liquid crystal layer is placed horizontally and irradiated from a direction inclined at an angle of 5 ° with respect to a vertical line with respect to the surface.

The intensity of selective reflection is determined as 5,520 cd / m ² . When an optical element composed of an L-circular polarizer and a liquid crystal cell for vertical alignment mode is arranged between the light source and the cholesteric liquid crystal layer, the intensity of selective reflection is reduced to 97 cd / m ² , It is 1/57 or less of the value, and a high contrast is obtained as in Example 2.

When only the L-circular polarizer is disposed on the sample of the cholesteric liquid crystal layer, the intensity of the reflected light is 106 cd / m ² . This means that most of the reflection of the optical element is the surface reflection of the L-circular polarizer itself. It is quite obvious that the anti-reflective coating removes this surface reflection and a fairly high contrast is expected in this system.

By applying a voltage of 3V and 5V are alternately in the liquid crystal cell for vertical alignment mode, each intensity of the selective reflection 471cd / ^{m 2} and 2,520cd / ^{m 2} results. This result shows that the intensity of selective reflection is controlled by combining vertically aligned liquid crystal cells.

The fluorescence intensity from the cholesteric liquid crystal layer is 18 cd / m ² without the optical element for suppressing selective reflection, and when 3 V and 5 V are applied to the liquid crystal cell for vertical alignment mode with the optical element, 3.6 cd / m ² respectively. And 7 cd / m ² . The fluorescence intensity is only 1 / 2.6 by using the combination of the L-circular polarizer and the liquid crystal cell for the vertical alignment mode, that is, the effect on the light emitted from the cholesteric liquid crystal layer of the optical element is It is small.

Example 4
A liquid crystal cell for twisted nematic (TN) mode is prepared. Two glass substrates with ITO electrodes patterned thereon and covered with a conventional / commercial polyimide alignment layer are fired and rubbed. They are assembled so that the rubbing directions of the two substrates form an angle of 90 °. The cell gap is set to 5 μm. Fill the cell with liquid crystal material “MLC-6424” from Merck KGaA. This liquid crystal has birefringence (Δn) 0.0928 and dielectric anisotropy (Δε) 10.6.

  The sample of the cholesteric liquid crystal layer prepared in Example 1 is again used as the luminescent cholesteric liquid crystal layer.

As described in Example 2, the substrate of the cholesteric liquid crystal layer is placed horizontally and irradiated from a direction inclined at an angle of 5 ° with respect to the normal to the surface. The intensity of selective reflection is measured as 3,670 cd / m ² . As with Example 2, when an optical element is introduced, it is reduced. By using an optical element composed of an L-circular polarizer and a liquid crystal cell for TN mode applying a voltage of 5 V, which is disposed between the light source and the cholesteric liquid crystal layer, the intensity of selective reflection is 3,670 cd / s. reduced from the value of m ² in 99CD / ^{m 2,} this is 1/37 or less of the value, high contrast is obtained.

When only the L-circular polarizer is disposed on the sample of the cholesteric liquid crystal layer, the intensity of the reflected light is 106 cd / m ² . Similar to Example 3, this means that most of the reflection of the optical element is a surface reflection of the L-circular polarizer itself.

Instead, application of a voltage of 0 V to the liquid crystal cell for TN mode (ie no voltage) results in a selective reflection intensity of 125 cd / m ² . This result shows that the intensity of selective reflection is controlled by combining vertically aligned liquid crystal cells.

The fluorescence intensity of the cholesteric liquid crystal layer is 11 cd / m ² without the optical element for the selective reflection suppressing a 3 cd / m ² when 0V is applied to the liquid crystal cell for TN mode has the optical element. By using an optical element comprising a combination of an L-circular polarizer and a liquid crystal cell for TN mode, the liquid crystal cell reduces the fluorescence intensity to 1 / 3.6 of the above value. This indicates that the optical element has a relatively small effect on the light emitted from the cholesteric liquid crystal layer.

Example 5
As in Example 2, the liquid crystal cell having the vertically aligned nematic liquid crystal prepared in Example 2 is used as the liquid crystal cell. The cholesteric liquid crystal layer produced in Example 1 is used as the cholesteric liquid crystal layer. The difference between Example 5 and Example 2 is that a cholesteric liquid crystal layer is used instead of a layer having a blue phase material, and an R-circular polarizer is used instead of an L-circular polarizer. . An R-circular polarizer is sandwiched between a cholesteric liquid crystal layer and a liquid crystal cell with a quarter wave plate facing the cholesteric liquid crystal layer. Furthermore, a liquid crystal cell is sandwiched between the R-circular polarizer and an additional linear polarizer having this transmission axis perpendicular to that of the R-circular polarizer.

In the same manner as in Example 2, a substrate on which a cholesteric liquid crystal layer is formed is placed horizontally and irradiated from a direction inclined at an angle of 5 ° with respect to a vertical line with respect to the surface. The intensity of selective reflection from the cholesteric liquid crystal layer itself is 660 cd / m ² . When an optical element comprising an R-circular polarizer, a vertical alignment mode liquid crystal cell and a linear polarizer is introduced between the light source and the cholesteric liquid crystal layer, the intensity of selective reflection from the cholesteric liquid crystal layer is reduced to 18 cd / m ² . To do. That is, it is 1/40 or less of the previous value. At the same time, high contrast can be obtained. When removing the cholesteric liquid crystal layer, the intensity of the reflected light is 15 cd / m ² . This reflected light is due to the surface reflection of the polarizer in the optical element itself and is therefore removed by the antireflection coating. Therefore, higher contrast is expected to be achieved. The intensity of the light from the selective reflection, 7V the liquid crystal cell having a vertically aligned, by applying respective voltages of 5V and 3V, respectively a ^{420cd / m 2, 360cd / m} 2 and 66 cd / ^{m 2.} This result clearly shows that the intensity of light from selective reflection is controlled by applying various voltages to the liquid crystal cell having the vertical alignment.

The fluorescence intensity of the cholesteric liquid crystal layer is 34 cd / m ² without the optical element for the selective reflection suppressing, when using an optical element for applying a voltage of 5V to the liquid crystal cell having a vertically aligned, to 10 cd / m ² Decrease. Thus, the fluorescence intensity is reduced by only 1/3 of its previous value by using a combination of R-circular polarizer, vertically aligned liquid crystal cell and linear polarizer. That is, the effect on the light emitted from the cholesteric liquid crystal layer of the optical element is very small. Further, by applying 3V and 0V voltage, respectively to the liquid crystal cell, the fluorescence intensity of 3 cd / ^{m 2} and 0.2 cd / ^{m 2} are respectively provided. This indicates that the fluorescence intensity is also controlled by applying various voltages to the liquid crystal cell having the vertical alignment.

Comparative Example 1
The experiment of Example 5 is repeated. However, here, an L-circular polarizer is applied to the switching element instead of the R-circular polarizer. Here, the intensity of selective reflection from the cholesteric liquid crystal layer is 660 cd / m ² . Then, an optical element including an L-circular polarizer, a vertical liquid crystal cell in a vertical alignment mode, and a linear polarizer is disposed between the light source and the cholesteric liquid crystal layer. This reduces the intensity of selective reflection from the cholesteric liquid crystal layer to 9 cd / m ² , that is, almost the same value as that obtained in Example 5. Even when a voltage in the range of 3V to 7V is applied to the liquid crystal cell in the vertical alignment mode, the intensity of selective reflection remains at a value of about 9 cd / m ² . Then, the optical element is applied 5V and 0V voltage to the respective vertical liquid crystal cell, respectively, the observed fluorescence intensity, respectively 5 cd / ^{m 2} and 0.2 cd / ^{m 2.} As a result, the combination of the L-circular polarizer, the liquid crystal cell and the linear polarizer used here reflects the light emitted from the cholesteric liquid crystal layer because the cholesteric liquid crystal layer cannot reflect the L circularly polarized light. It clearly shows that light cannot be used. Therefore, the light use efficiency is not improved at the same time while suppressing the selective reflection of the element in the black state.

FIG. 3 is a cross-sectional view of an electro-optic switching element according to a first preferred embodiment of the present invention including a film having one or more Brewster angles that suppresses selective reflection of a cholesteric liquid crystal layer. FIG. 5 is a cross-sectional view of a second preferred embodiment of an electro-optic switching element that is another electro-optic switching element of the present invention including a film having one or more Brewster angles that suppresses selective reflection of a cholesteric liquid crystal layer. .

An electro-optic switching element according to a third preferred embodiment of the present invention, comprising a film having one or more Brewster angles that suppresses selective reflection of a cholesteric liquid crystal layer, each comprising one or more parts FIG. FIG. 6 is a diagram illustrating the angle β as a function of the angle α for different values of the refractive index n between the normal of the display surface and polarized light having an electric vector oscillating parallel to the entrance surface of the film having a Brewster angle. is there.

Shows the angle γ as a function of the angle α for different values of the refractive index n between the normal of the display surface (perpendicular to the film) and the polarized light emitted from the cholesteric liquid crystal layer of the film having a Brewster angle FIG. It is sectional drawing of the 4th preferable aspect which suppresses the selective reflection of the cholesteric liquid crystal layer using the liquid crystal layer which has vertical alignment.

FIG. 6 is a cross-sectional view of a fifth preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal phase that is aligned / operated in a twisted nematic mode. FIG. 6 is a cross-sectional view of a sixth preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal phase that is aligned / operated in a hybrid alignment nematic mode.

FIG. 9 is a cross-sectional view of a seventh preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal phase that is aligned / operated in a bend alignment nematic mode. FIG. 10 is a cross-sectional view of an eighth preferred embodiment of the present invention that suppresses selective reflection of a cholesteric liquid crystal layer using a liquid crystal phase that is aligned / operated in an in-prene switching type liquid crystal mode.

Explanation of symbols

101 A film 102 having a structure having one or two or more Brewster angles θ _B A linear polarizer 103 A quarter-wave plate 104 in a wide wavelength range 104 A cholesteric liquid crystal layer 105 A light scattering layer 106 Oscillates parallel to the incident surface Incident polarized light 107 having an electric vector Incident polarized light 108 having an electric vector oscillating perpendicular to the incident plane Circularly polarized light 109 emitted from a cholesteric liquid crystal layer Light absorbing layer

201 A film 202 having a structure having one or two or more Brewster angles θ _B A linear polarizer 203 A quarter-wave plate 204 in a wide wavelength range 204 A cholesteric liquid crystal layer 205 A light scattering layer 206 Oscillates parallel to the incident surface Incident polarized light 207 having an electric vector Incident polarized light 208 having an electric vector oscillating perpendicularly to the incident plane 208 Circularly polarized light emitted from a cholesteric liquid crystal layer

301 Transparent substrate 302 supporting a film having a structure having one or more Brewster angles θ _B Linear polarizer 303 Quarter wavelength plate 304 in a wide wavelength range Cholesteric liquid crystal layer 305 Light scattering layer 306 Incident surface Incident polarized light 307 having an electric vector oscillating parallel to the incident light 308 Incident polarized light 308 having an electric vector oscillating perpendicular to the incident plane Circularly polarized light 309 emitted from the cholesteric liquid crystal layer 309 A wedge 310 having a different angle α from the Brewster angle θ _B Film with star angles θ _B and α

601 Liquid crystal 602 Quarter wavelength plate 603 of wide wavelength range Linear polarizer 604 Light scattering layer 605 Cholesteric liquid crystal layer 606 Circularly polarized light 607 rotating in the same direction as the cholesteric liquid crystal layer Circularly polarized light 608 rotating in a direction different from the cholesteric liquid crystal layer Circularly polarized light emitted from a cholesteric liquid crystal layer

701 Liquid crystal 702 Quarter wavelength plate 703 in a wide wavelength range Linear polarizer 704 Light scattering layer 705 Cholesteric liquid crystal layer 706 Circularly polarized light 707 rotating in the same direction as the cholesteric liquid crystal layer Circularly polarized light 708 rotating in a different direction from the cholesteric liquid crystal layer Circularly polarized light emitted from a cholesteric liquid crystal layer

801 Liquid crystal 802 Quarter wavelength plate 803 of wide wavelength range 803 Linear polarizer 804 Light scattering layer 805 Cholesteric liquid crystal layer 806 Circular polarized light 807 rotating in the same direction as the cholesteric liquid crystal layer Circular polarized light 808 rotating in a different direction from the cholesteric liquid crystal layer Circularly polarized light emitted from a cholesteric liquid crystal layer

901 Liquid crystal 902 Quarter wavelength plate 903 in a wide wavelength range Linear polarizer 904 Light scattering layer 905 Cholesteric liquid crystal layer 906 Circularly polarized light 907 rotating in the same direction as the cholesteric liquid crystal layer Circularly polarized light 908 rotating in a different direction from the cholesteric liquid crystal layer Circularly polarized light emitted from a cholesteric liquid crystal layer

1001 Liquid crystal 1002 A quarter-wave plate 1003 in a wide wavelength range 1003 Linear polarizer 1004 Light scattering layer 1005 Cholesteric liquid crystal layer 1006 Circularly polarized light 1007 rotating in the same direction as the cholesteric liquid crystal layer Circularly polarized light 1008 rotating in a different direction from the cholesteric liquid crystal layer Circularly polarized light emitted from a cholesteric liquid crystal layer 1009 Electrode having an alternating potential

Claims (31)

An electro-optic switching element comprising: a cholesteric liquid crystal including at least one light-emitting portion; and an optical component capable of removing or reducing selective reflection of the cholesteric liquid crystal.   The electro-optic switching element according to claim 1, wherein a helical pitch of the cholesteric liquid crystal coincides with an optical path length of light emitted from the light emitting portion. An optical component that can eliminate or reduce selective reflection is
An optical component having one angle that is essentially a Brewster angle or more than one angle that is essentially a Brewster angle, and an optical component capable of converting linearly polarized light into circularly polarized light. Item 3. The electro-optical switching element according to Item 1 or 2.   The electro-optic switching element according to claim 3, wherein the optical component capable of removing or reducing the selective reflection of the cholesteric liquid crystal comprises a polymer layer. An optical component that can eliminate or reduce the selective reflection of cholesteric liquid crystals,
-Including a liquid crystal layer,
A polarizer is not included between the cholesteric liquid crystal and the liquid crystal layer, and an optical component on the opposite side of the liquid crystal layer from the cholesteric liquid crystal layer (the optical component can convert circularly polarized light into linearly polarized light), and the essence A polarizer having a transmission axis parallel to the electric field plane of linearly polarized light,
The electro-optic switching element according to claim 1. The liquid crystal layer of the optical component capable of removing or reducing the selective reflection of the cholesteric liquid crystal has the following orientation-twisted nematic,
The electro-optic switching element according to claim 1, wherein the electro-optic switching element is a liquid crystal layer selected from one having hybrid alignment nematic or vertical alignment nematic. An optical component that can eliminate or reduce the selective reflection of cholesteric liquid crystals,
-Including a liquid crystal layer,
-An optical component is included on the side facing the cholesteric liquid crystal layer capable of converting circularly polarized light having the same twist direction as the cholesteric liquid crystal layer into linearly polarized light, and-the transmission axes sandwiching the liquid crystal layer are perpendicular to each other Including two linear polarizers and a transmission axis of the polarizer close to a cholesteric liquid crystal layer parallel to the electric field plane of linearly polarized light converted from circularly polarized light,
The electro-optic switching element according to claim 1. A liquid crystal layer of an optical component capable of removing or reducing the selective reflection of cholesteric liquid crystal is a liquid crystal layer of the following group-in-plane switching type liquid crystal layer,
-Fringe field switching liquid crystal layer,
The electro-optic switching element according to claim 7, which is a liquid crystal layer selected from a ferroelectric liquid crystal layer or a ferroelectric liquid crystal polymer.   The electro-optic switching element according to any one of claims 1 to 8, wherein a gap between the cholesteric liquid crystal and an optical component capable of removing or reducing selective reflection of the cholesteric liquid crystal is 0.1 mm or less.   The electro-optic switching element according to claim 1, wherein the total thickness of optical components capable of converting circularly polarized light into linearly polarized light is 0.1 mm or less.   11. A light emitting device according to any of claims 1 to 10, comprising three light emitting means, each for light emission of one of three of three different wavelengths, each of said three means forming each of three layers. Electro-optic switching element.   The electro-optic switching element according to claim 1, comprising light emitting means having three different regions, each having a different emitter, each for light emission of three different wavelengths. 13. The electro-optic switching element according to claim 12, wherein each of the three different regions for light emission at each of three different wavelengths has an extension of 90.000 [mu] m < ² > or less.   The electro-optic switching element according to claim 1, comprising means for scattering light.   15. The electro-optic switching element according to claim 14, wherein the means for scattering light is a sheet having a plurality of regions having a refractive index different from that of the surrounding material.   The electro-optic switching element according to claim 14 or 15, wherein the means for scattering light is a polymer dispersed liquid crystal (PDLC) or includes PDLC.   17. The electro-optic switching element according to claim 16, wherein the polymer dispersed liquid crystal is electrically addressable, preferably for switching between a light scattering state and a transparent state.   5. An optical medium having one angle that is essentially a Brewster angle or more than one angle that is essentially a Brewster angle, can act as a means for scattering light. Electro-optic switching element.   The electro-optic switching element according to claim 1, wherein at least one surface of the cholesteric liquid crystal containing at least one light-emitting portion is covered with a light absorption layer.   The side of the cholesteric liquid crystal facing the optical component capable of removing or reducing the selective reflection of the cholesteric liquid crystal is covered with a layer that is not transparent to circularly polarized light having a rotation opposite to the twist direction of the cholesteric liquid crystal. The electro-optic switching element according to claim 1.   21. The electro-optic switching element according to claim 20, wherein the layer that is not transparent to circularly polarized light having a rotation opposite to the twisted direction of the cholesteric liquid crystal is a half mirror.   21. The layer that is not transparent to circularly polarized light having a rotation opposite to the twist direction of the cholesteric liquid crystal comprises a linear polarizer having at least one surface covered with a quarter wave plate. Electro-optic switching element.   The electro-optic switching element according to claim 22, wherein the linear polarizer is made of a wire grid. Use of the electro-optic switching element according to any of claims 1 to 23 for display information.   Use of the electro-optic switching element according to any of claims 1 to 23 in an electro-optic display.   An electro-optic display comprising one or more electro-optic switching elements according to claim 1.   27. A display device comprising one or more electro-optic displays according to claim 26.   27. Use of an electro-optic display according to claim 26 for display information.   A method of manufacturing a membrane or plate having a structure having one or more Brewster angles with subunits, wherein the subunits are constructed to protrude from a support or substrate.   24. The method for manufacturing an electro-optic switching element according to claim 1, wherein means for removing or reducing selective reflection of the cholesteric liquid crystal is incorporated.   27. The method of manufacturing an electro-optic display according to claim 26, wherein means for removing or reducing selective reflection of the cholesteric liquid crystal is incorporated.

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