JP2004326131A - Circularly polarized light extracting optical device, its manufacturing method, polarizing light source device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circularly polarized light extracting optical device where a liquid crystal layer is laminated so that an optical singular point is not caused without necessitating an adhesive and a peeling stage. <P>SOLUTION: The circularly polarized light extracting optical device 10 consists of first to third liquid crystal layers 12, 14 and 16, and is constituted so that the directions of the directors of the liquid crystal molecules 18 of the respective liquid crystal layers on boundaries 13 and 15 between the first and the second liquid crystal layers and the second and the third liquid crystal layers are aligned. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a circularly polarized light extraction optical element capable of continuously laminating a plurality of polymerized liquid crystal layers having cholesteric regularity while substantially matching the directions of directors of liquid crystal molecules, a method of manufacturing the same, and a method of manufacturing the same. The present invention relates to a polarized light source device and a liquid crystal display device using a polarized light extraction optical element.

  For example, there is a circularly polarized light extraction plate that uses a cholesteric liquid crystal layer to reflect right-handed or left-handed circularly polarized light having a wavelength corresponding to the helical pitch of the liquid crystal molecules and transmits the other.

  In such a circularly polarized light extraction plate, as a method of broadening the bandwidth of the wavelength selectively reflected, a plurality of cholesteric liquid crystal layers having different helical pitches are disclosed, for example, as disclosed in Patent Document 1 and Patent Document 2. Some are stacked.

  Further, as a polarized light source device or a liquid crystal display device using such a circularly polarized light extraction plate, for example, there is one disclosed in Patent Document 3 or the like.

  The circularly polarized light extraction plate disclosed in Patent Document 2 is configured by bonding a plurality of cholesteric liquid crystal layers that have been formed into a film in advance using a plurality of layers, an adhesive, or by thermally bonding without using an adhesive. I have.

  When an adhesive is used, the adhesiveness between the liquid crystal molecules of the liquid crystal layer formed into a film and the molecules of the adhesive needs to be good, and not only the type of the adhesive is limited, but also the adhesive layer The thickness increases, and furthermore, there is a problem that reflection occurs at the interface between the adhesive layer and the liquid crystal layer due to a difference in refractive index between the two layers, and the extracted light is colored by the adhesive layer itself. Was.

  In the case of heat bonding without using an adhesive, it is necessary to heat the liquid crystal layer formed into a film to a glass transition temperature (Tg) or higher in order to give flexibility. In addition, there is a problem that industrialization is difficult, and further heating at a high temperature causes the liquid crystal molecules of the liquid crystal layer to mix randomly with the liquid crystal molecules of the adjacent liquid crystal layer, thereby deteriorating the optical characteristics. There are problems such as.

  Furthermore, in either case of using or not using an adhesive, an alignment film and a base material must be used to align liquid crystal molecules in a planar manner, and the entire thickness is increased by the thickness. There is.

  On the other hand, when a stretched film such as a stretched PET (polyethylene terephthalate) film is used as a base material, the stretched film itself has the function of an alignment film, so that the alignment film can be omitted. Only the thickness increases the overall thickness.

  Furthermore, when an alignment film and a base material are used, it is conceivable that the liquid crystal is separated after solidification. However, there is a problem that the liquid crystal layer is often damaged at the time of separation and mass productivity is reduced. .

  In the case where three or more liquid crystal layers are stacked, any of the above-mentioned methods requires a considerably complicated process, and there is a problem that the substrate and the alignment film are wasted by the number of layers.

  To solve the above problems, for example, as disclosed in Patent Document 4, a method has been proposed in which another cholesteric liquid crystal polymer is coated on a cholesteric liquid crystal polymer layer to form a circularly polarized light extraction layer. I have.

JP-A-8-271731 JP-A-11-264907 JP-A-9-304770 JP-A-11-44816

  However, in the method of Patent Document 4, it is difficult to always keep the helical axis of the cholesteric liquid crystal molecules in each liquid crystal layer constant. The direction of the director is not determined unambiguously, causing a fault in the direction of the director of the liquid crystal molecules at the interface of the cholesteric liquid crystal polymer layer, deteriorating the optical function as a circularly polarized light extraction optical element. was there.

  The present invention has been made in view of the above-mentioned conventional problems, and does not require an adhesive or a peeling step, and continuously laminates circles while substantially matching the directions of directors of liquid crystal molecules. An object of the present invention is to provide a polarized light extraction optical element, a manufacturing method thereof, a polarized light source device using the circularly polarized light extraction optical element, and a liquid crystal display device.

  According to the present invention, a plurality of liquid crystal layers formed by three-dimensionally cross-linking liquid crystal molecules having cholesteric regularity are stacked in a state in which the directions of the helical axes of the liquid crystal molecules substantially coincide with each other. The object is achieved by a circularly polarized light extraction optical element characterized in that the directions of the directors of the three-dimensionally crosslinked liquid crystal molecules near the interface are substantially matched.

  Further, in the liquid crystal layer, a distance per one pitch of a molecule helix in a helical structure of liquid crystal molecules may be different from a distance per one pitch of a molecule helix in a helical structure of liquid crystal molecules of another liquid crystal layer.

  Further, the thickness of each of the liquid crystal layers may be smaller than a thickness required for reflecting one of the right-handed or left-handed circularly polarized light components of the corresponding wavelength light incident thereon at the maximum reflectance.

  Further, a plurality of liquid crystal layers containing liquid crystal molecules having cholesteric regularity are stacked in a state where the direction of the helical axis of the liquid crystal molecules substantially coincides with each other. The distance per pitch is different from the distance per one pitch of the molecule helix in the helical structure of the liquid crystal molecules of the other liquid crystal layer, and the distance per one pitch of the molecule helix is between the liquid crystal layer and the other liquid crystal layer. A transition liquid crystal layer that changes in the thickness direction is arranged, and a distance per one pitch of a molecule helix of liquid crystal molecules in the transition liquid crystal layer is substantially equal to a distance per one pitch of a molecule helix on one adjacent liquid crystal layer. The above object is achieved by a circularly polarized light extraction optical element characterized in that the distance is equal to a distance per one pitch of the molecular spiral on the liquid crystal layer side. Than it is.

  Still further, the selective reflection wavelength bands of at least two of the liquid crystal layers may have different center regions and partially overlap end regions.

  The invention of the present production method is to coat a polymerizable monomer molecule or a polymerizable oligomer molecule, which is a liquid crystal molecule having cholesteric regularity, on an alignment film, to align the liquid crystal molecule by its alignment force, and to apply the polymerizable monomer molecule or The polymerizable oligomer molecules are three-dimensionally cross-linked to form a liquid crystal layer, and a polymerizable monomer molecule or a polymerizable oligomer molecule, which is a separately prepared liquid crystal molecule having cholesteric regularity, is directly coated thereon. The procedure of aligning the coated liquid crystal molecules using the alignment force of the cross-linked liquid crystal layer surface and forming the next liquid crystal layer by three-dimensional cross-linking is repeated, and the liquid crystal layers are sequentially laminated to form a multilayer. The above object is achieved by a method for producing a circularly polarized light extraction optical element characterized by the following.

  As described above, if the directions of the directors of the adjacent layers are substantially the same, the circularly polarized light reflection characteristic peculiar to the cholesteric structure can be sufficiently brought out. If the director directions do not substantially match, an optical singularity will be formed, and when measuring the spectral reflectance using circularly polarized light, a point that is discontinuous with respect to the wavelength will be Occurs.

  The three-dimensional cross-linking means that polymerizable monomer molecules or polymerizable oligomer molecules are three-dimensionally polymerized with each other to form a network structure. By adopting such a state, the cholesteric liquid crystal state can be optically fixed, a stable film at room temperature can be obtained, and handling as an optical film becomes easy.

  When a polymerizable monomer molecule or a polymerizable oligomer molecule is formed into a liquid crystal layer at a predetermined temperature, the liquid crystal layer is in a nematic state. However, if an arbitrary chiral agent is added to the liquid crystal layer, a chiral nematic liquid crystal (cholesteric liquid crystal) is obtained. In the invention of the present production method, a chiral agent is added in an amount of several% to 10%. The selective reflection wavelength band of the cholesteric liquid crystal can be controlled by changing the chiral power by changing the type of the chiral agent or by changing the concentration of the chiral agent.

  In addition, if the distance per one pitch of the molecular helix is different in each layer, it is possible to extract circularly polarized light of light at an arbitrary wavelength.

  In particular, the thickness of each layer is made thinner than the thickness required to reflect one of the right-handed or left-handed circularly polarized light components of the corresponding wavelength light incident thereon at the maximum reflectance, and the one circularly polarized light component is more than the maximum reflectance. If one of the circularly polarized light components is reflected at a small reflectance, it can be used for various optical devices that can take out the one circularly polarized light component at an arbitrary reflectance or transmittance.

  If a transition liquid crystal layer in which the distance per one pitch of the molecular helix changes is provided between each liquid crystal layer, the optical characteristics can be made smooth.

  If the turning directions of the liquid crystal molecules in each liquid crystal layer are the same, generation of an optical tomographic layer between the liquid crystal layers can be avoided.

  In particular, if at least two liquid crystal layers do not overlap the center of the selective reflection wavelength, a continuous broadband can be achieved.

  The invention of the polarized light source device includes a light source that generates non-polarized light, and any one of the above-described circularly polarized light extraction optical elements that receives non-polarized light from the light source and transmits circularly polarized light. The above object is achieved by a polarized light source device.

  In addition, the invention of a liquid crystal display device includes the above-mentioned polarized light source device, and a liquid crystal cell which receives polarized light from the polarized light source device and transmits the light by changing the transmittance for the polarized light. The above object is achieved by a liquid crystal display device.

  In the present invention, the liquid crystal molecules are aligned by directly coating the next liquid crystal layer on the surface of the previously formed liquid crystal layer having an alignment force, so that the liquid crystal molecules are aligned. The direction of the director of each liquid crystal molecule is substantially matched. Therefore, an optical singular point does not occur.

  Since the present invention is configured as described above, it is possible to extract any circularly polarized light, and when the extracted wavelength band is equal to or more than a certain value, it is possible to obtain circularly polarized light in a continuous wavelength band without forming a fault in the middle. It has an excellent effect.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the circularly polarized light extraction optical element 10 according to the embodiment of the present invention is configured such that the helical axis 18A of the liquid crystal molecule 18 having a cholesteric regularity has a helical structure in a layer direction. A first liquid crystal layer 12, a second liquid crystal layer 14, and a third liquid crystal layer 16, which are three-dimensionally cross-linked in a state of being aligned in the thickness direction, are directly stacked in this order, and As schematically shown in FIG. 2A or 2B, each interface 13 of the first liquid crystal layer 12 and the second liquid crystal layer 14 and the second liquid crystal layer 14 and the third liquid crystal The direction of the director D of the liquid crystal molecules 18 in the vicinity of each interface 15 of the layer 16 is substantially matched. The state of the three-dimensionally crosslinked polymer can be referred to as a network structure (network structure).

  As the liquid crystal molecules 18 included in the first to third liquid crystal layers 12 to 16, those having cholesteric regularity such as cholesteric liquid crystal and chiral nematic liquid crystal are used.

  The cholesteric liquid crystal layer generally exhibits an optical rotation selection characteristic of separating a rotation component in one direction and a rotation component in the opposite direction based on a physical molecular arrangement, but has a helical axis in a planar arrangement. Is split into two circularly polarized lights, right-handed light rotation and left-handed light rotation, one of which is transmitted and the other is reflected.

  This phenomenon is known as circular dichroism, and when the direction of rotation of circularly polarized light is appropriately selected with respect to incident light, circularly polarized light having the same direction of rotation as the helical axis of the cholesteric liquid crystal is selectively reflected. .

  The maximum optical rotation scattering in this case occurs at the wavelength λO of the following equation (1).

.lambda.o = nav * p (1)
Here, p is a helical pitch, and nav is an average refractive index in a plane orthogonal to the helical axis.

  The wavelength bandwidth Δλ of the reflected light at this time is expressed by the following equation (2).

Δλ = Δn * p (2)
Here, Δn is a birefringence value.

  Each liquid crystal layer is formed using a monomer or oligomer of the liquid crystal molecules 18 that are three-dimensionally crosslinked.

  When a crosslinkable monomer molecule is used as a specific material of the cholesteric liquid crystal, a mixture of a liquid crystalline monomer and a chiral compound as disclosed in JP-A-7-158638 and JP-T-10-508882 is used. When using an oligomer molecule, a cyclic organopolysiloxane compound having a cholesteric phase as disclosed in JP-A-57-165480 is desirable.

  When a light-transmitting substrate is used as the substrate instead of the glass substrate 20, polymethyl methacrylate, a homo- or copolymer of an acrylate or methacrylate such as polymethyl acrylate, polyethylene terephthalate, A sheet-shaped or plate-shaped member made of a transparent resin such as polyester such as polyethylene terephthalate, polycarbonate, or polyethylene, or a transparent material such as transparent ceramics may be used.

  In the first to third liquid crystal layers 12, 14, 16 as described above, the liquid crystal molecules 18 having cholesteric regularity are directed in the direction of the director D as schematically shown in FIGS. However, the liquid crystal layer continuously rotates in the thickness direction of the liquid crystal layer to form a spiral structure.

  Here, the direction of the director D of the liquid crystal molecules 18 near the interfaces 13 and 15 is substantially coincident with each other, as shown in FIG. This means that the directions of the liquid crystal molecules 18 are almost the same or, as shown in FIG. This is often due to the inability to optically distinguish the head and tail of the liquid crystal molecules.

  As described above, if the direction of the director D of the liquid crystal molecules 18 in each layer substantially coincides on both sides of the interfaces 13 and 15 of the liquid crystal layer, the circularly polarized light reflection characteristic peculiar to the cholesteric structure at this position is obtained. No faults occur. If the directions of the directors D do not substantially match, an optical singular point will be formed, and when the circularly polarized light extraction optical element 10 is measured using circularly polarized light, reflection will occur. Discontinuous points occur at wavelengths.

  Whether or not the directions of the directors D of the liquid crystal molecules are substantially the same can be determined by observing the cross section of the liquid crystal layer with a transmission electron microscope. When a cross section of a layer in which liquid crystal molecules having cholesteric regularity are solidified is observed with a transmission electron microscope, light and dark stripes corresponding to pitches specific to the cholesteric structure can be observed. Therefore, if the liquid crystal layers adjacent to each other can be observed at substantially the same density (bright and dark) at the portions where they contact each other, that is, at the interface, the directions of the directors D of the liquid crystal molecules near the interface between the adjacent liquid crystal layers substantially match. Will be.

  Next, a description will be given of a manufacturing method for forming the circularly polarized light extraction optical element 10 so that the directions of the directors D of the liquid crystal molecules 18 substantially coincide with each other at the interface between the adjacent liquid crystal layers.

  The first manufacturing method is shown in FIG.

  First, as shown in FIG. 3A, an alignment film 22 is formed on a glass substrate 20, and then, as shown in FIG. Coat possible monomer molecules or polymerizable oligomer molecules.

  The coated liquid crystal molecules are aligned by the alignment force of the alignment film 22 to form the first liquid crystal layer 12. As shown in FIG. 3 (C), this is polymerized (by the action of a photoinitiator added in advance and ultraviolet rays radiated from outside, or by electron beam irradiation) to perform three-dimensional crosslinking (polymerization). I do.

  On the solidified first liquid crystal layer 12, the same polymerizable monomer molecules or polymerizable oligomer molecules as described above are directly coated as shown in FIG. The coated liquid crystal molecules are aligned with the liquid crystal molecules on the surface of the solidified first liquid crystal layer 12 by the alignment force on the surface thereof, and the liquid crystal molecules are aligned to form the second liquid crystal layer 14.

  At this time, the interaction between the solidified surface of the liquid crystal layer 12 and the liquid crystal molecules of the second liquid crystal layer 14 is an important key. That is, when the liquid crystal molecules of the first and second liquid crystal layers approach each other, the respective director directions are substantially matched or substantially 180 °.

  If the director directions do not substantially match, an optical singularity will be formed, and when measuring the spectral reflectance using circularly polarized light, a point that is discontinuous with respect to the wavelength will be Occurs.

  As shown in FIG. 3E, the second liquid crystal layer 14 is solidified by three-dimensional cross-linking (polymerization) by irradiating ultraviolet rays or electron beams to the second liquid crystal layer 14 in the same manner as described above. Form. In this way, the required number of liquid crystal layers are sequentially stacked.

  In the case of this method, the polymerizable monomer molecule or the polymerizable oligomer molecule may be dissolved in a solvent to form a coating solution. In this case, a drying step for evaporating the solvent before three-dimensional crosslinking is required. Become.

  Next, a circularly polarized light extraction optical element 30 according to a second embodiment of the present invention shown in FIG. 4 will be described.

  In the circularly polarized light extraction optical element 30, the distances p1 and p2 of the liquid crystal molecules per pitch of the liquid crystal in the first liquid crystal layer 32 and the second liquid crystal layer 34 formed by the above-described manufacturing method are different. Things.

  Here, the distance per one pitch of the molecular helix refers to the distance p1 in the thickness direction necessary for the orientation (director) direction of the liquid crystal molecules in each liquid crystal layer to make one rotation with respect to the central axis of the molecular helix. p2 (see FIG. 4).

  As described above, when the distances of the liquid crystal layers in the stacked liquid crystal layers per one pitch of the molecular helix are made different, circularly polarized light having different wavelengths can be extracted, and the wavelength bandwidth can be widened.

  Next, a circularly polarized light extraction optical element 40 according to a third embodiment of the present invention shown in FIG. 5 will be described.

  The circularly polarized light extraction optical element 40 has three layers of first to third wavelengths, λ1, λ2, and λ3, which are different from each other in the distance of each liquid crystal molecule per pitch of the molecular helix. The third liquid crystal layers 42, 44, and 46 are stacked in the same manner as described above.

  Note that FIG. 5 shows that the liquid crystal layers 42, 44, and 46 reflect a part of the right-handed circularly polarized light R and transmit the left-handed circularly polarized light L.

  The thickness of each of the first to third liquid crystal layers 42, 44, 46 is smaller than the thickness for obtaining the maximum reflectance in each liquid crystal layer, for example, assuming that the pitch is 8 pitches of the molecular helix. The thickness is four pitches.

  The thickness of each of the first to third liquid crystal layers 42, 44, 46 is smaller than the thickness for obtaining the maximum reflectance in each liquid crystal layer, for example, assuming that the pitch is 8 pitches of the molecular helix. The thickness is four pitches.

  The polarization separation effect of the cholesteric liquid crystal is such that, in the cholesteric liquid crystal, one of the right-handed or left-handed circularly polarized light components of light in the wavelength band width Δλ centered on the wavelength λo is reflected, and the other circularly polarized light component and other Light in the wavelength range is transmitted. Upon reflection, right (left) or left (right) circularly polarized light is reflected as it is.

  Generally, in order to reflect one of the right-handed or left-handed circularly polarized light components at the maximum reflectance (usually 95% to 99%) and transmit the other, at least eight pitches are required. .

  On the other hand, the pitch number of each liquid crystal layer is 6.4 pitch, which is smaller than the required pitch number. Therefore, in the range of Δλ, the reflected light amount of one of the right-handed or left-handed circularly polarized light is reduced by 80%. , The amount of transmitted light can be 20%. The transmittance of the other circularly polarized light component is improved as compared with the case where the number of pitches of the cholesteric structure is eight, and is close to 100%.

  For example, if the pitch number of each polymerized liquid crystal layer is 5.6, for example, the reflected light amount of one of the right-handed or left-handed circularly polarized light components in each liquid crystal layer is 70%, and the transmitted light amount is similarly It can be 30%. That is, an arbitrary reflectance and transmittance with respect to the maximum reflectance can be obtained by the pitch number of each liquid crystal layer.

  Generally, in order to reflect one of the right-handed or left-handed circularly polarized light components at the maximum reflectance (usually 95% to 99%) and transmit the other, light having a wavelength of 380 nm in the visible light region is used. For light having a wavelength of at least 1.6 μm and 780 nm, at least 3.3 μm is required.

  On the other hand, the thickness of each liquid crystal layer having the cholesteric structure in FIG. 5 is, for example, 1.24 μm (380 nm) to 2.6 (780 nm) μm in the visible light region (the thickness of each layer is selected. (Change linearly with respect to the reflection wavelength).

  Therefore, in the range of Δλ, the reflected light amount of one of the right-handed or left-handed circularly polarized light can be 80% and the transmitted light amount can be 20%. The transmittance of the other circularly polarized light component is improved as compared with the case where the thickness is 5 μm, and is close to 100%.

  Further, for example, when the thickness of each liquid crystal layer is, for example, 1.1 μm (380 nm) to 2.3 (780 nm) μm (linearly changing with respect to the thickness selective reflection wavelength of each layer), The amount of reflected light of one of the right-handed or left-handed circularly polarized light components in the liquid crystal layer can be 70%, and the amount of transmitted light can be 30%. That is, it is possible to obtain an arbitrary reflectance and transmittance with respect to the maximum reflectance depending on the thickness of each liquid crystal layer.

  Further, the circularly polarized light extraction optical element is configured to be thinner than when each layer reflects one of right-handed or left-handed circularly polarized light components at the maximum reflectance, so that the incident light for forming the reflected light and The same circularly polarized light component as the reflected light can be obtained by the transmitted light incident from the opposite side.

  The circularly polarized light extraction optical element 40 shown in FIG. 5 is such that the first to third liquid crystal layers 42, 44, and 46 have different reflection wavelengths, but the present invention is not limited to this. As in the circularly polarized light extraction optical element 50 according to the fourth example of the embodiment shown in FIG. 6, the reflection wavelengths of the first, second, and third liquid crystal layers 52, 54, and 56 are the same. Is also good. Here, a part of the left-handed circularly polarized light L is reflected in the second liquid crystal layer 54 so as to be different from the first and third liquid crystal layers 52 and 56.

  In this way, right-handed and left-handed circularly polarized light of a predetermined wavelength can be simultaneously extracted at an arbitrary ratio.

  Next, a circularly polarized light extraction optical element 60 according to a fifth embodiment of the present invention shown in FIG. 7 will be described.

  The circularly polarized light extraction optical element 60 has a transition liquid crystal layer 66 provided between first and second liquid crystal layers 62 and 64 having different distances per one pitch of a molecular helix.

Here, the distance per one pitch of the molecular helix between the first and second liquid crystal layers 62 and 64 is p1
, P2, and when the distance per one pitch of the molecular helix of the transition liquid crystal layer 66 is ps, p1 <p2 and p1 ≦ ps ≦ p2 are satisfied.

  That is, the distance of the molecular helical pitch of the transition liquid crystal layer 66 is changed in the thickness direction so that p1 at the interface 63 with the first liquid crystal layer 62 and p2 at the interface 65 with the second liquid crystal layer 64. Have been. Specifically, when the second liquid crystal layer 64 is coated on the first liquid crystal layer 62, the first liquid crystal layer 62 is slightly melted. This makes it possible to broaden the wavelength of the extracted circularly polarized light continuously.

  In the case where liquid crystal layers having different molecular helical pitches are stacked as in the circularly polarized light extraction optical element 30 shown in FIG. 4, as shown in FIG. When a part of the wavelengths is made to overlap, that is, at least two of the stacked liquid crystal layers have different center regions C1 and C2 of the selective reflection wavelength band, and one end regions E1 and E2 are different from each other. When they are overlapped, the wavelength of the extracted circularly polarized light can be continuously broadened.

  The circularly polarized light extraction optical elements 10, 30, 40, 50, and 60 according to each example of the above embodiment are used for a polarized light source device 80, for example, as shown in FIG.

  In the polarized light source device 80, for example, the above-described circularly polarized light extraction optical element 84 (10, 30, 40, 50 or 60) is attached to the light exit surface side of the surface light source device 82 that generates non-polarized light, and Is configured to extract circularly polarized light.

  Such a polarized light source device 80 is used, for example, as a light source of a liquid crystal display device 90 as shown in FIG.

  This liquid crystal display device 90 is composed of the above-mentioned polarized light source device 80 and a liquid crystal cell 92 provided on the polarized light exit surface side and transmitting the light by changing the transmittance for circularly polarized light of a predetermined wavelength. ing.

  Next, Example 1 of the present invention will be described with reference to some comparative examples. In Example 1, the director was matched by rubbing.

  Having a polymerizable acrylate at both ends, a nematic-isotropic transition temperature having a spacer between the mesogen in the center and the acrylate, a monomer molecule 90 parts having a temperature of 110 ° C., and a polymerizable acrylate at both ends. The chiral nematic liquid crystal was dissolved in a rubbing direction of ± 5 degrees on the alignment film by dissolving 10 parts of the chiral agent molecules in a toluene solution and adding 5% by weight of a photoinitiator to the monomer molecules. That the directors are aligned).

  On the other hand, a transparent glass substrate was coated with a polyimide dissolved in a solvent by spin coating, dried, formed at 200 ° C. (0.1 μm in thickness), and rubbed to function as an alignment film.

  The glass substrate with an alignment film was set on a spin coater, and the toluene solution was spin-coated.

  Next, toluene was evaporated at 80 ° C., and further, the presence of a cholesteric layer was visually confirmed by selective reflection.

  The above-mentioned coating film was irradiated with ultraviolet rays, and the acrylate of the monomer molecule was three-dimensionally crosslinked by radicals generated from the photoinitiator to be polymerized (film thickness 2 μm). When measured with a spectrophotometer, the center wavelength of the selective reflection band was around 600 nm.

  Furthermore, the surface of the polymerized coating film can be calculated by the director direction of the coating film surface (this direction can be calculated from the rubbing direction of the alignment film, the selective reflection wavelength of the cholesteric liquid crystal, the refractive index of the cholesteric liquid crystal, and the film thickness). Then, it can be measured optically, and the cross section can be confirmed with a transmission electron microscope.)

  Further, the same toluene solution as described above except that the amount of the chiral agent molecule was 15 parts was spin-coated on the rubbed coating film at a higher rotation speed than the previous time.

  Next, toluene was evaporated at 80 ° C., and further, the presence of a cholesteric layer was visually confirmed by selective reflection. When measured with a spectrophotometer, the center wavelength of the selective reflection band was around 500 nm.

  The coating film was irradiated with ultraviolet rays to three-dimensionally crosslink the acrylate of the monomer molecule with radicals generated from the photoinitiator to polymerize (1.5 μm thickness).

  Observation of the cross sections of the obtained coating films having a plurality of cholesteric structures with a transmission electron microscope revealed that the light and dark patterns between the polymerized liquid crystal layers were in a state parallel to each other. And no fault was observed between the layers (this indicates that the directions of the directors of the liquid crystal molecules between the adjacent liquid crystal layer surfaces coincided). Further, when measured by a spectrophotometer, no optical singularity was observed in the transmittance.

(Comparative Example 1)
In Comparative Example 1, the directors were mismatched by rubbing.

  The procedure was the same as in Example 1 except that the surface of the polymerized coating film was rubbed in a direction at 90 degrees from the director direction of the coating film surface.

  Observation of the cross sections of the obtained coating films having a plurality of cholesteric structures with a transmission electron microscope revealed that the light and dark patterns between the polymerized liquid crystal layers were in a state parallel to each other. However, a fault was observed between the layers (this indicates that the directions of the directors of the liquid crystal molecules between adjacent liquid crystal layer surfaces do not match). Further, when measured with a spectrophotometer, an optical singular point was observed in the transmittance, and when examined in detail, the state of circularly polarized light was disturbed.

  In Example 2, the directors were matched by direct lamination.

  The procedure was the same as in Example 1 except that the polymerized coating was not rubbed.

  Observation of the cross sections of the obtained coating films having a plurality of cholesteric structures with a transmission electron microscope revealed that the light and dark patterns between the polymerized liquid crystal layers were in a state parallel to each other. There was no fault (this indicates that the directions of the directors of the liquid crystal molecules between the adjacent liquid crystal layer surfaces coincided). Further, when measured by a spectrophotometer, no optical singularity was observed in the transmittance.

  Having a polymerizable acrylate at both ends, a nematic-isotropic transition temperature having a spacer between the mesogen in the center and the acrylate, a monomer molecule 90 parts having a temperature of 110 ° C., and a polymerizable acrylate at both ends. Was dissolved in a toluene solution, and 3% by weight of a photoinitiator was added to the monomer molecules. (The chiral nematic liquid crystal had a rubbing direction of ± 5 degrees on the alignment film. That the directors are aligned).

  On the other hand, a transparent glass substrate was coated with a polyimide dissolved in a solvent by spin coating, dried, formed at 200 ° C. (0.1 μm in thickness), and rubbed to function as an alignment film.

  The glass substrate with an alignment film was set on a spin coater, and the toluene solution was spin-coated.

  Next, toluene was evaporated at 80 ° C., and further, the presence of a cholesteric layer was visually confirmed by selective reflection.

  The coating film was irradiated with 1/10 of the ultraviolet ray of Example 1, and the acrylate of the monomer molecule was three-dimensionally crosslinked by radicals generated from the photoinitiator to polymerize (film thickness 2 μm). When measured with a spectrophotometer, the center wavelength of the selective reflection band was around 600 nm.

  Further, the same toluene solution as described above except that the chiral agent molecule was 15 parts was spin-coated on the polymerized coating film at a higher rotation speed than the previous time.

  Next, toluene was evaporated at 80 ° C., and further, the presence of a cholesteric layer was visually confirmed by selective reflection. When measured with a spectrophotometer, the center wavelength of the selective reflection band was around 500 nm.

  The coating film was irradiated with ultraviolet rays to three-dimensionally crosslink the acrylate of the monomer molecule with radicals generated from the photoinitiator to polymerize (1.5 μm thickness).

  Observation of the cross sections of the obtained coating films having a plurality of cholesteric structures with a transmission electron microscope revealed that the light and dark patterns between the polymerized liquid crystal layers were in a state parallel to each other. There was no fault (this indicates that the directions of the directors of the liquid crystal molecules between the adjacent liquid crystal layer surfaces coincided). Further, when measured by a spectrophotometer, no optical singularity was observed in the transmittance.

  Further, a transition layer having a light and dark pattern was observed between the layers. In the transition layer, the pitch of the light and dark patterns matched the adjacent layer, and the transition layer was in an intermediate state in the transition layer.

  The reason for the formation of the transition layer is that the first layer is not completely three-dimensionally cross-linked by reducing the amount of the photoinitiator added or the amount of UV irradiation, and the components of the first layer are partially added to the second layer. Probably because of mass transfer.

FIG. 1 is an enlarged schematic diagram illustrating a circularly polarized light extraction optical element according to a first example of an embodiment of the present invention. Schematic diagram showing directors of liquid crystal molecules in the circularly polarized light extraction optical element FIG. 4 is an enlarged schematic cross-sectional view showing a first method for manufacturing a circularly polarized light extraction optical element according to the present invention. FIG. 2 is a schematic diagram showing an enlarged main part of a circularly polarized light extraction optical element according to a second example of an embodiment of the present invention. Enlarged schematic sectional view showing a circularly polarized light extraction optical element according to a third example of the embodiment. Enlarged schematic cross-sectional view showing a circularly polarized light extraction optical element according to a fourth example of the embodiment. FIG. 9 is a schematic diagram showing an enlarged circularly polarized light extraction optical element according to a fifth example of the embodiment. 12 is a diagram showing a reflection wavelength band of the circularly polarized light extraction optical element according to the second example of the embodiment. Schematic enlarged sectional view showing an example of an embodiment according to a polarized light source device. Enlarged schematic cross-sectional view illustrating an example of an embodiment of a liquid crystal display device.

Explanation of reference numerals

10, 30, 40, 50, 60, 70 ... circularly polarized light extraction optical element 12, 32, 42, 52, 62 ... first liquid crystal layer 13, 15, 63, 65 ... interface 14, 34, 44, 54, 64 ... second liquid crystal layer 16, 46, 56 ... third liquid crystal layer 18 ... liquid crystal molecules 20 ... glass substrate 22 ... alignment film 66 ... transition liquid crystal layer 80 ... polarized light source device 82 ... surface light source device 90 ... liquid crystal display device 92 … Liquid crystal cell D… Director

Claims (12)

  A plurality of liquid crystal layers in which liquid crystal molecules having cholesteric regularity are three-dimensionally cross-linked are stacked in a state in which the directions of the helical axes of the liquid crystal molecules substantially coincide with each other. A circularly polarized light extraction optical element, wherein the directions of directors of the dimensionally cross-linked liquid crystal molecules are substantially the same.   2. The liquid crystal layer according to claim 1, wherein a distance per one pitch of a molecular helix in the helical structure of the liquid crystal molecules is different from a distance per one pitch of a molecular helix in the helical structure of the liquid crystal molecules of the other liquid crystal layer. Circularly polarized light extraction optical element.   3. The liquid crystal display device according to claim 1, wherein the thickness of each of the liquid crystal layers is smaller than a required thickness for reflecting one of the right-handed or left-handed circularly polarized light components of the corresponding wavelength light incident thereon at the maximum reflectance. And a circularly polarized light extraction optical element.   A plurality of liquid crystal layers containing liquid crystal molecules having cholesteric regularity are stacked in a state where the directions of the helical axes of the liquid crystal molecules substantially coincide with each other. Is different from the distance per one pitch of the molecular helix in the helical structure of the liquid crystal molecules of the other liquid crystal layer, and the distance per one pitch of the molecular helix between the liquid crystal layer and the other liquid crystal layer is the thickness. A transition liquid crystal layer that changes in direction is arranged, and a distance per one pitch of a molecule helix of liquid crystal molecules in the transition liquid crystal layer is substantially equal to a distance per one pitch of a molecule helix on one adjacent liquid crystal layer; The circularly polarized light extraction optical element, wherein a distance per one pitch of the molecular helix is substantially equal on the liquid crystal layer side.   5. A circle according to claim 1, wherein the selective reflection wavelength bands of at least two of the liquid crystal layers are bands having different center regions and partially overlapping end regions. Polarization extraction optical element.   6. The circularly polarized light extraction optical element according to claim 1, wherein a direction of a helical axis of the liquid crystal molecules is a thickness direction of the liquid crystal layer.   7. A circularly polarized light extraction optical element according to claim 1, wherein adjacent liquid crystal layers are in contact with each other.   A polymerizable monomer molecule or a polymerizable oligomer molecule, which is a liquid crystal molecule having cholesteric regularity, is coated on an alignment film, and the liquid crystal molecules are aligned by the alignment force. Crosslinking to form a liquid crystal layer, and then directly coating a polymerizable monomer or polymerizable oligomer molecule, which is a separately prepared liquid crystal molecule having cholesteric regularity, on the three-dimensionally crosslinked liquid crystal layer surface. Circularly polarized light extraction characterized by repeating the procedure of aligning the coated liquid crystal molecules using force and forming the next liquid crystal layer by three-dimensionally cross-linking, successively laminating the liquid crystal layers to form a multilayer. A method for manufacturing an optical element.   9. The method according to claim 8, wherein a direction of a helical axis of liquid crystal molecules of the liquid crystal layer is a thickness direction of the liquid crystal layer.   The method according to claim 8, wherein adjacent liquid crystal layers are in contact with each other.   8. A light source for generating non-polarized light, and a circularly polarized light extraction optical element according to claim 1 which receives non-polarized light from the light source and transmits circularly polarized light. Polarized light source device.   A liquid crystal display device comprising: the polarized light source device according to claim 11; and a liquid crystal cell that receives polarized light from the polarized light source device, and transmits the polarized light by changing the transmittance for the polarized light.

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