JP4433394B2 - Information recording display film and method for producing the same - Google Patents

Description

  The present invention relates to a film manufacturing method capable of modulating polarized light with high efficiency, and an information recording / displaying film for effectively recording information such as characters and images and presenting information.

An interference pattern recording and reproducing method using laser interference will be described based on a hologram known as an element to which an optical interference phenomenon is applied.
A conventional example of an optical system for recording a hologram is shown in FIG. The light emitted from the laser 1901 is divided into two light beams by a beam splitter 1902, and each light beam is reflected using mirrors 1903 and 1904. The light beam from the mirror 1903 is spread using an objective lens 1906 and then irradiated onto a recording object 1907 as object light 1909. The reflected light from this is irradiated onto the recording material 1908.
Further, another light beam reflected by the mirror 1904 is spread by the objective lens 1905 and then irradiated to the recording material 1908 as reference light 1910. Accordingly, the light intensity distribution resulting from the superposition of the object 1909 and the reference light 1910 is recorded on the recording material 1908. This light intensity distribution is recorded as 1000-7000 very fine and complicated striped patterns per 1 mm. This fringe is called an interference fringe, which is caused by a phenomenon called interference that strengthens and weakens each other as a result of overlapping the laser light into two parts and then superimposing them again as object light 1909 and reference light 1910. Yes.

  Next, how interference occurs will be described by replacing it with familiar phenomena. When two pebbles are thrown into the pond at the same time, two waves are generated, and the phenomenon of interference occurs when they are combined. Where the amplitude is large, that is, where the peaks and peaks of the waves coincide, the two waves are added and become even higher (strengthening interference), and where the peaks of one wave and the valleys of the other wave match. Is subtracted and lowered (weakening interference). These interference effects change the height of water waves and increase or decrease the sound intensity of sound waves. In the case of light, the pebbles correspond to point light sources that emit light of the same wavelength, and the brightness, that is, the intensity of light, changes due to interference from light from two point light sources that emit light of the same wavelength. A bright and dark pattern called interference fringes is formed in the space. The stripe pattern changes depending on the setting conditions of the optical system such as the relative positional relationship between the two light sources or the shape of the object to be recorded.

Laser light is used to record holograms because the laser light is single-wavelength light, and only when this light is divided into two and superimposed again, it is stable in time and space. This is because interference fringes are obtained.
If the object has a three-dimensional shape as indicated by 1907, the object light 1909 is a superposition of the light emitted from each point on the surface, and its wavefront is not a simple spherical wave but a complex wavefront. It becomes. Therefore, the interference fringes actually recorded on the recording material 1908 is a superposition of patterns called zone plates made up of light and shade stripes formed when each point light source is an object light, and forms a very complicated pattern. It will be.

Consider what happens when light is applied to the hologram recorded on the recording material 1908. Here, attention is paid to the vicinity of a point on the recording material 1908 on which a complicated pattern is recorded. Then, the pattern at that point is a light and dark stripe having a fine interval, and can be considered as a kind of diffraction grating. A diffraction grating is usually a surface of a glass plate in which a large number of fine parallel lines are engraved, and is often used as an element for performing spectroscopy or deflecting light. When light is applied to the diffraction grating, most of the light passes through the diffraction grating and travels straight, but the light is emitted in a different direction. This is a phenomenon of diffraction, and the direction is the direction of whether the light emerging from the adjacent transparent portion is delayed or advanced by one wavelength. The light exiting in these directions is in a state of constructive interference, and the direction indicates the same direction as the object light.
In other words, for an observer who has his eyes in the direction of light coming out, the object 1907 having a three-dimensional shape is reproduced exactly as it is, so that the same shape as the object at the same position as the object is present. You can see the image.

In such a diffracting action of the light of the hologram, a recording material having a thicker recording material than the density interval corresponding to the recorded intensity distribution is known as a volume hologram. Detailed analysis including calculation of theoretical diffraction efficiency of the volume hologram is performed in Non-Patent Document 1.
The Bragg diffraction condition is applied by configuring this type to have a periodic structure in the thickness direction. This is because when light having a certain wavelength is incident on each layer forming a periodic structure, the light scattered by each layer causes a phenomenon in which the scattering component intensifies in a specific direction corresponding to the wavelength, the incident angle, and the pitch between the layers. . This is called Bragg's diffraction condition. Such a condition has a three-dimensional configuration compared to the conventional two-dimensional diffractive optical element, and acts as blazing (converging light in one direction). Will have. Therefore, the diffraction efficiency can be drastically improved with respect to the conventional diffractive optical element, and theoretically 100% efficiency is possible. In fact, a high efficiency of 90% or more can be expected even when losses in the middle are taken into consideration.

  As described above, since the hologram can converge light in one direction with high efficiency, it can be applied to light control or image reproduction and modulation. In addition, since information such as the shape of an object is recorded as a complicated pattern using an interference action, it is also used for information security purposes for concealing or encrypting original information.

In recent years, information equipment such as an optical pickup for a DVD and a liquid crystal display has widely used a method utilizing a polarization action for recording and display. Accordingly, various optical devices such as a half mirror and a polarization beam splitter for performing polarization modulation and separation action on the laser light as the light source have been required inside the optical pickup apparatus corresponding to these recording media. . Conventionally, as these optical devices, bulk prisms made of glass have been used.
The inside of such a prism has a cube shape filled with a liquid or a solid for refractive index matching with the dielectric multilayer film. With respect to such a prism structure, in order to increase the degree of polarization separation, it is necessary to form multiple dielectric multilayer films, and there is a problem that the manufacturing cost is increased. The separation membrane is disposed at 45 ° in order to bend the light propagation direction by 90 °. For this reason, the size of the separation element in the thickness direction is fixed by the size of the separation film constituting one prism. For this reason, in response to the recent demands for ultra-thin and small-size information equipment, optical devices used in these devices are required to be further reduced in size and thickness, but these requirements must be satisfied. There was also a problem that it was not possible.

In such situations, micro optical devices such as holograms that have been applied to the reproduction of stereoscopic images, etc. can be made as thin as a film, and laser light can be obtained by utilizing the light diffraction phenomenon. Can be modulated with high efficiency. In particular, since the volume type diffractive optical element can theoretically achieve diffraction efficiency up to 100%, it can be expected to have various applications for information recording and display as described above.
Therefore, for example, as described in Non-Patent Document 2, the diffraction phenomenon of the hologram element is used to improve the visibility by separating the direction of the reflected light and the display image on the display surface of the liquid crystal display device. There are attempts that have been made. However, the type of hologram used here does not have the function of preferentially modulating light polarized in a specific direction from the liquid crystal screen, and efficient use of light for polarized light is not possible. The problem that it was not possible remained.

  For example, Patent Document 1 and Patent Document 2 report the production of a diffractive optical element in which a polarization dependency with respect to specific polarized light is generated using a liquid crystal material. However, these diffractive optical elements show large dependence only on specific polarized light, but it is possible to produce an element that satisfies both the large polarization dependence and diffraction efficiency characteristics for arbitrary polarized light. There was a problem that it was not done. Furthermore, there is a problem that a simple and inexpensive manufacturing method cannot be applied to a thin base material such as a large-area film.

H. Kogelnik, (BellSyst. Tech. J., 48, 1969, P.2909-2947) “Design of Hologram for Brightness Enhancement in Color LCDs”, G. T. Valliath, SID98 DIGESET, 44.5L, P1139 Japanese Patent Laid-Open No. 11-271536 JP 2000-212465 A

  The present invention solves the above-described problems of the prior art, has a large polarization area with a large polarization dependency with respect to an arbitrary polarization direction, and has a large area that can be used for recording and displaying information such as characters and images. It is an object to provide a method that can be manufactured at low cost.

As a result of studies to achieve the above object, the following information recording / display film manufacturing method has been achieved. That is, the present invention
(1) A light modulation means in a state where a sample containing liquid crystal and one or more polymerizable substances selected from a monomer, an oligomer, and a polymer is sealed in a region sandwiched between transparent substrates, and then stress is applied to the transparent substrate Information on alignment of liquid crystal molecules along the direction of stress applied to the transparent substrate in a region where a polymerizable substance is partially cured, which is irradiated with a light beam having a plurality of periodic intensity distributions A method for producing a recording display film.
(2) The method for producing a film for information recording display according to (1), wherein the stress is a tensile stress along a direction substantially parallel to the transparent substrate.
(3) The method for producing a film for information recording display according to (2), wherein the tensile stress applied to the transparent substrate is performed by stretching the transparent substrate.
(4) The method for producing a film for information recording display according to (1), wherein the light modulation means is performed by light transmittance modulation.
(5) The method for producing a film for information recording display according to (1), wherein the light modulation means is performed by phase modulation of a light beam.
(6) The method for producing a film for information recording display according to (1), wherein the light flux has a polarization state substantially perpendicular or horizontal to a periodic direction of intensity distribution.
(7) The method for producing a film for information recording display according to (1), wherein the viscosity of the sample is controlled by a viscosity control means.
(8) The method for producing a film for information recording display according to (7), wherein the viscosity control means is a temperature change.
(9) The method for producing a film for information recording display according to (8), wherein the viscosity of the sample is controlled to approximately 3 Pa · s or less by a viscosity control means.
(10) The information recording / displaying film according to any one of (2), (3), and (6), wherein the direction of stress applied to the transparent substrate is substantially equal to the direction of polarization of the irradiated light beam. Manufacturing method.
(11) The method for producing a film for information recording display according to (1), wherein the sample contains a photopolymerization initiator and a pigment.
(12) The region where the polymerizable substance is partially cured by irradiation with a light beam having a plurality of periodic intensity distributions in the previous period exists in a plurality of islands on the transparent substrate. Manufacturing method of information recording display film.
(13) The method for producing a film for information recording display according to (12), wherein the plurality of island-shaped regions have an asymmetric shape stretched in a stress application direction.
(14) The method for producing a film for information recording display according to (1), wherein the light intensity of the luminous flux is generally larger than 3 mW / cm ² .

(15) A surface including a liquid crystal and one or more polymerizable substances selected from a monomer, an oligomer, and a polymer is sealed in a region sandwiched between transparent substrates, and then a surface having periodic irregularities on the transparent substrate. Pressurizing a heated object having a shape, for information recording display in which liquid crystal molecules are aligned along a periodic direction composed of irregularities on the surface of the object in a region where the polymerizable substance is partially thermoset A method for producing a film.
(16) The film for information recording display according to (15), wherein the heating temperature of the object having a surface shape composed of periodic irregularities is a temperature at which the viscosity of the sample is approximately 3 Pa · s or less. Production method.
(17) The method for producing an information recording / displaying film according to (15), wherein the uneven shape of the object surface has a large uneven shape with respect to the interval of the periodic structure.
(18) The method for producing an information recording / displaying film according to (17), wherein the uneven shape on the surface of the object has a size approximately equal to or larger than a period interval.
(19) The method for producing an information recording / displaying film according to (15), wherein the sample contains a thermal polymerization initiator.
(20) The information recording according to (15), wherein a region where the polymerizable substance is partially heat-cured by pressure bonding of an object composed of periodic irregularities is present in a plurality of islands on the transparent substrate. Manufacturing method of display film.
(21) The method for producing a film for information recording display according to (20), wherein the plurality of island-shaped regions have an asymmetric shape extending in a periodic direction of the uneven shape of the object.
It is.

  The present invention has a large polarization dependency with respect to an arbitrary polarization direction, and is a highly efficient light modulation film that can be used for information recording and display of characters, images, etc., and a method for manufacturing the film with a large area at a low cost. Can be provided. For this reason, the importance of information recording fields, image display fields, etc. will increase in the future, and it can be widely applied to areas where large market development is expected and has great value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
In Embodiment 1, a case where a glass substrate is used as a transparent substrate prior to the present invention and a sample for information recording display is manufactured without applying stress to the glass substrate will be described.
First, the relationship between the production process and the formation mechanism of the information recording / displaying film will be clarified using the system shown in FIG. 1, and the process of establishing the manufacturing method will be described in detail based on the experimental results.
First, as a transparent substrate for the sample 107, a glass substrate having a size of about 1 inch was used from the viewpoint of easy handling in an experiment. The sample preparation process used in the optical system shown in FIG. 1 mainly includes the following four processes.
(1) The glass substrate is heated to about 35 to 65 ° C. with a hot plate.
(2) A sample (mixed with liquid crystal, monomer, oligomer, photopolymerization initiator, dye, and beads) is dropped onto glass.
(3) The sample is sandwiched between another glass substrate.
(4) Fix the glass substrate with the sample holder.

  Here, the sample will be described. As liquid crystal, TL or BL series made by Merck, and as a polymerizable substance such as a monomer or oligomer, for example, urethane prepolymer, dimethylol tricyclodecane diacrylate, 2hydroxyethyl methacrylate, etc. made by Kyoeisha Chemical Co., Ltd. can be used. . For example, N-phenylglycine or the like can be used as a photopolymerization initiator, and dibromofluorescein or the like can be used as a pigment.

Next, an experimental apparatus and method for applying laser interference exposure and forming a fine periodic structure inside using the sample 107 created here will be described.
As the laser 101 for interference exposure, a semiconductor-excited solid green laser (λ = 532 nm, 20 mw) was used. In addition, a half-wave plate 102 and an ND (neutral density) filter 103 are provided for the light after laser emission so that the polarization direction of the laser light and the intensity of the light can be arbitrarily adjusted.
The laser beam is expanded to a diameter of about 20 mm by the beam collimator 104 and divided into two by the half mirror 106. One of the two divided beams was adjusted by the mirror 105 so as to be condensed on the sample 107 at an intersection angle of 30 degrees. The sample 107 is placed on a stage that can be maintained at a set temperature by the Peltier element 114 and the temperature control device 115.

  Furthermore, simultaneously with the formation of the element by interference exposure from the front of the sample, light of a long-wavelength randomly polarized He-Ne laser 116 (λ = 632.8 nm, 5 mW) that is not exposed to the element is incident from the back of the sample, and this is exposed. In addition, it was configured to be usable as a monitor beam for observing the phenomenon occurring inside the sample. When the lattice structure is formed inside the element, the He—Ne laser light 116 incident from the back surface generates diffracted light corresponding to the state. This diffracted light beam is split into P-polarized light and S-polarized light by a polarizing beam splitter 111 (PBS) and received by photodetectors 108 and 109. Each light intensity change with time can be observed on the computer 113 via the interface board 112 in real time.

  An element was actually manufactured using the system shown in FIG. 1, and the relationship between the laser interference exposure time and the change in the diffracted light intensity was observed while changing some set temperatures of the sample 107. The results are shown in FIGS. FIG. 2 shows the case where the sample 107 is irradiated with the state of light emitted from the laser 101 as S-polarized light. In the optical system shown in FIG. 1, the S-polarized light refers to the case where the vibration axis of the laser beam exists in the vertical direction perpendicular to the surface plate on which the laser is placed, while the P-polarized light refers to the surface plate. This is defined as the case where the vibration axis of the laser beam is generated in the parallel horizontal direction.

2 and 3, (a), (b), and (c) show the results when the holding temperature of the sample 107 is 20 ° C., 35 ° C., and 50 ° C., respectively. First, in FIG. 2A, the S-polarized light starts to increase about 50 seconds after the start of the laser exposure, and then the light intensity of the P-polarized light increases. When about 100 seconds elapse, the light intensity almost reaches a saturation value. Among the diffracted light intensity, the S-polarized light component is about 180 μW at the maximum, while the diffracted light intensity of P-polarized light is about 50 μW. When production is attempted at about 20 ° C., which is about room temperature, it can be seen that the ratio of the diffracted light intensity to S-polarized light, which is the same as the polarization state of the laser 101 used for interference exposure, is larger than that of P-polarized light.
In the case of (b), the S-polarized diffraction component starts to increase first after about 25 seconds, and the P-polarized diffraction component starts to be generated after about 10 seconds. The light intensity of each component continues to increase, but after about 50 seconds, the light intensity of the P-polarized component overtakes the light intensity of S-polarized light and continues to increase greatly. Eventually, the diffraction intensity of P-polarized light increases to around 300 μW, while S-polarized light is saturated at about 150 μW, and the diffraction component for P-polarized light is about twice as large.
In (c), the S-polarized light starts increasing in about 20 seconds from the start, and the P-polarized component starts increasing slightly later. The S-polarized light and the P-polarized light continue to increase in the same manner until the time of about 35 seconds, but after that, the light intensity of the P-polarized light component starts to increase sharply until about 50 seconds have elapsed, and finally reaches a little over 600 μW. Increases and saturates. On the other hand, the light intensity of the S-polarized component began to decrease, and decreased to only a few μW after about 50 seconds.

  In this way, when laser interference exposure is performed with the laser 101 in the S-polarized state, when the temperature is as low as about 20 ° C., the diffraction component of the S-polarized light is large, and when the temperature is increased to about 35 degrees, The light intensity of the P-polarized component is reversed to S-polarized light and increases. When the temperature was further increased to about 50 ° C., the diffraction intensity of the P-polarized component showed a very large increase whereas the light intensity of the S-polarized component was decreased from the middle. In order to confirm the reproducibility, the experiment was performed several times under the same condition setting, but all showed the same tendency. From these experiments, it was clarified that the magnitude of the observed diffraction intensity and the ratio of its components vary greatly depending on the holding temperature of the sample 107.

Next, a description will be given of the result of performing laser interference exposure in which the polarization state of the laser 101 is changed by 90 degrees using the half-wave plate 102 as shown in FIG. In FIG. 3A, the increase of P-polarized light starts about 30 seconds after the start of laser exposure, and then the increase of S-polarized light starts about 10 seconds later. Thereafter, the light intensity of the P-polarized light reaches a saturation value of 80 μW after about 70 seconds. On the other hand, the increase rate of the diffracted light intensity of the S-polarized light is gradual compared with the P-polarized light, and reaches a saturation value at about 20 μW at the maximum. Compared with the case of FIG. 2 in the case where the production is attempted at 20 ° C., which is about room temperature, this time, the diffracted light intensity ratio of the P-polarized component is larger than that of the S-polarized light. This is a result that the ratio of the diffracted light intensity to the P-polarized light, which is the same as the polarization state of the laser 101 used for the interference exposure this time, is large.
Next, in the case of (b), the diffracted light intensity starts to increase for both P-polarized light and S-polarized light after about 25 seconds. The P-polarized component continues to increase rapidly to about 100 seconds as it is, and finally increases in intensity to near 400 μW and saturates. S-polarized light showed a gradual increase and then saturated in about 50 seconds. The maximum intensity was slightly less than 50 μW, which was about one-tenth of that of P-polarized light.
In (c), both P-polarized light and S-polarized light start to increase in about 20 seconds from the start, but P-polarized light tends to rise slightly earlier. Thereafter, both S-polarized light and P-polarized light continue to increase in the same manner until the time of about 35 seconds. Thereafter, the light intensity of the P-polarized light component starts to increase rapidly after about 50 seconds, and finally reaches a little over 800 μW. Increases and saturates. On the other hand, the light intensity of the S-polarized component began to decrease, and decreased to only a few μW after about 50 seconds.

In this way, when laser interference exposure is performed with the laser 101 in the P-polarized state, when the temperature is as low as about 20 ° C., the diffraction intensity of the P-polarized light is about four times larger than the diffraction intensity component of the S-polarized light. When the temperature is further increased to about 35 ° C., this ratio is further increased, and the light intensity of the P-polarized component is about 10 times that of the S-polarized component. When the temperature was increased to about 50 ° C., the diffraction intensity of the P-polarized component showed a very large increasing tendency, whereas the light intensity of the S-polarized component decreased from the middle. The experiment in this case was performed a plurality of times under the same condition setting, but all showed the same tendency. When interference exposure was performed with a P-polarized laser, the light intensity of the P-polarized component increased and the S-polarized component decreased as the temperature was increased as in FIG. However, the behavior of each polarization component was different from the case of FIG.
From the experimental results using the sample 107 as described above, it was found that the holding temperature of the sample and the polarization state of the laser to be irradiated have a great influence on the diffraction efficiency characteristics in the manufacturing process of the information recording display film.

  Next, in order to clarify the influence of temperature, the relationship between the viscosity of the sample and the temperature, which is a factor that greatly changes the characteristics due to temperature change, was investigated. FIG. 4 shows the measurement result of the dynamic viscoelasticity value when the temperature of the sample is gradually increased from 20 ° C. near the room temperature using the dynamic viscoelasticity measuring apparatus. From FIG. 4, the viscosity of the sample shows a high viscosity of 10 Pa · s or more at around 20 ° C., but when it exceeds 30 ° C., it decreases to about 1/3, approximately 4 Pa · s, and the temperature increases to around 50 ° C. Then, it turns out that it has further decreased to the low value of 1 Pa.s or less.

Each of the temperature values such as 20 ° C., 35 ° C., and 50 ° C., in which the viscosity value of the sample in FIG. 4 shows a large change, is the difference in the diffraction efficiency behavior described in FIGS. It can be seen that it generally corresponds to the holding temperature. In order to analyze these results in more detail, FIG. 5 shows a model of the relationship between the lapse of laser interference exposure time at 50 ° C. and the change in the diffracted light intensity, in which the polarization dependence is very large. As a result of manufacturing the device using the system shown in FIG. 1, the relationship between the passage of interference exposure time and the change in diffracted light intensity can be broadly classified into the following three processes.
(1) A period from the start of laser irradiation until the increase of the light intensity of P-polarized light or S-polarized light starts.
(2) A period in which the light intensity increases similarly for both P-polarized light and S-polarized light.
(3) A period in which the P-polarized light intensity increases rapidly and reaches a saturation value, while the S-polarized light decreases to nearly zero.

  Next, the formation of a fine periodic structure inside the sample and the alignment process of the liquid crystal in these processes will be described with reference to FIG. (A) shows a cross-sectional view of the sample 107, and this surface is irradiated with a periodic light intensity distribution formed by laser interference exposure such as 601. FIG. At this time, a polymerizable substance that causes a photocuring reaction such as a monomer or an oligomer in the sample enclosed by the transparent substrate 603 is accelerated by irradiation with light energy of a certain level or more, and is applied to a portion having a high light intensity. Start to aggregate. The process until this reaction starts corresponds to the period (1) in FIG.

  Next, monomers, oligomers and the like aggregated in a portion having a high light intensity are photocured to be polymerized, and a photocured polymer layer 604 corresponding to the position of the bright portion of the light intensity distribution indicated by 601 starts to be formed. In addition, a light-induced layer separation process occurs in which the liquid crystal molecules 602 gather in a portion with low light intensity so as to be extruded from the cured layer and form the liquid crystal layer 605. In this state, the liquid crystal molecules in the liquid crystal layer are considered to be randomly oriented. This process corresponds to the period (2) in FIG.

  Subsequently, the liquid crystal molecules of the liquid crystal layer are stretched under stress that is pulled from both sides by the shrinkage action accompanying photocuring in the polymer layers at both ends. At this time, in the liquid crystal layer, there is a localized region called a droplet, in which liquid crystal molecules are dispersed to form a lump, and this region corresponds to a dark part where the laser interference exposure intensity is weak, so that photocuring is slow. As a result, the polymer network formed is subjected to a force stretched on both sides. Therefore, an asymmetric network structure is formed that is pulled in the direction of the transparent substrate, which is the horizontal direction in the cross-sectional view of FIG. That is, it can be considered that liquid crystal molecules are aligned in a direction perpendicular to the photocured polymer layer 604 shown in FIG. 6C, which is a direction along the network structure formed in a stretched manner. Due to this liquid crystal alignment process, the polarization dependence in the device is manifested, and the phenomenon that the diffracted light intensity component of P-polarized light increases rapidly and conversely the diffracted light intensity of S-polarized light appears, which is shown in (3) of FIG. It is considered to correspond to the period.

As shown in FIG. 2 and FIG. 3, the change in the diffracted polarization component differs depending on the holding temperature of the sample because the viscosity value of the sample used depends greatly on the temperature as shown in FIG. This is considered to be because of having. At a temperature around 20 ° C., the photoinduced layer separation process is hindered by the viscosity of the sample and is not sufficiently accelerated, and the refractive index distribution corresponding to the interference exposure intensity distribution of the laser does not easily occur. It seems not to be a big value.
In addition, the difference in the polarization component of the diffracted light intensity appears depending on the polarization state of the laser to be irradiated. The polymerizable substance that exhibits a photocuring reaction, such as a monomer or oligomer in the sample, is irradiated with linearly polarized light. Among the randomly oriented molecules, the molecules having the main chain (or side chain) of the molecule oriented in the polarization direction mainly absorb light, and curing by photoreaction is promoted. For this reason, networking by photocuring tends to be formed in a direction along the polarization direction of the irradiated light. For this reason, it is considered that in the initial reaction process, the intensity of diffracted light with a polarization component that coincides with the polarization direction of the irradiated laser is preferentially increased.

At this time, if the sample is kept at a low temperature such as near room temperature, the photo-induced layer separation process is not accelerated, and the tensile stress due to the shrinkage of the cured polymer layer also affects the network structure in the liquid crystal layer. Therefore, alignment of liquid crystal molecules is not performed properly. As a result, it is considered that after a relatively small polarization dependency with respect to a polarized light component that coincides with the polarization direction of the irradiated laser occurs, the reaction is almost completed as it is.
When the holding temperature of the sample is increased, in the initial reaction, priority is given to the diffraction intensity component in the direction that matches the polarization state at the time of laser irradiation, but as the reaction proceeds, the effect of decreasing the sample viscosity due to temperature increase is demonstrated. First, the light-induced layer separation process is promoted, and the network structure in the liquid crystal layer is defined by the tensile stress due to the shrinkage of the cured polymer layer. For this reason, in FIG. 2B, at the start of the reaction, the diffraction intensity of the S-polarized light that matches the polarization state of the laser is large, but as the reaction time proceeds, the magnitude of the diffraction intensity component changes from S-polarized light to P-polarized light. In the end, it is explained that the polarization dependence due to P-polarized light increases.

In addition, comparing the processes of FIG. 2 and FIG. 3C, it can be seen that the polarization dependence is more apparent in FIG. This is because when the polarization state of the laser during interference exposure and the direction in which the liquid crystal is finally aligned coincide with each other, the initial polarization dependence is promoted as it is, and the alignment of the liquid crystal is more neatly aligned. As a result, it is considered that the polarization dependence can be greatly generated. FIG. 7 shows the measurement of the three reaction times in FIG. 5 when the intensity of the laser 101 in FIG. 1 is changed by the ND filter 103 in order to investigate the relationship between the laser irradiation intensity and the sample formation process. It is the result of having gone. (A)-(c) in a figure respond | corresponds to the reaction time of the period of (1)-(3) of FIG. It can be seen that in each reaction process, when the laser irradiation intensity is increased, the reaction time decreases exponentially and is almost saturated at an intensity of 3 mW / cm ² or more. From this result, it is considered that if the laser intensity is set to 3 mW / cm ² or more, the reaction can be completed in a short time, and the sample can be efficiently produced.

  FIG. 8 shows the result of observing a cross section of the produced sample with a scanning electron microscope (SEM). Note that the element after cutting was subjected to ultrasonic cleaning in methanol, and the liquid crystal was observed from the cross section. (B) shows an enlarged view of a part of the lattice structure of (a), and (c) shows a model diagram of the polymer network 803 of the liquid crystal layer 802 corresponding to (b). As can be seen from (b), it can be confirmed that the polymer network in the liquid crystal layer has an asymmetric structure that is flattened as a result of being pulled and stretched from the polymer layers at both ends. Further, as shown in FIG. 3C, when a droplet state in which liquid crystal molecules are aligned and aligned along the direction in which the polymer network is formed is formed inside as shown in FIG. It is possible to explain that such a large polarization dependency occurs.

  FIG. 9 shows an optical system for measuring the optical characteristics of the manufactured sample 903. In this optical system, randomly polarized light emitted from a He—Ne laser 901 (λ = 632.8, 5 mW) is converted into linearly polarized light (P-polarized light or S-polarized light) by a polarizing plate 902 and incident on a sample 903, and transmitted from the element. The diffraction efficiency of the sample 903 is measured by simultaneously detecting light and diffracted light with the two photodetectors 905 and 906 and measuring with the photodetector 907. The sample 903 is fixed to an automatic rotation stage 904, and this stage is controlled by a pulse drive controller.

The diffraction efficiency was calculated by dividing the diffracted light and transmitted light intensities thus obtained by the light intensity incident on the sample 903. The measurement results are shown in FIG. (A) is a sample produced with the laser polarization state as S-polarized light and corresponds to FIG. 2 (c), and (b) is produced using P-polarized light and FIG. It is a sample corresponding to c). ● indicates the diffraction efficiency when P-polarized light is incident, and ■ indicates the diffraction efficiency when S-polarized light is incident. In (a), it can be seen that the diffraction efficiency for P-polarized light is a little over 75%, indicating a very high diffraction efficiency. On the other hand, the diffraction efficiency for S-polarized light was about 0.3%, and it was confirmed that most components were transmitted. From these results, it can be seen that the ratio of the first-order diffraction efficiency of the P-wave and the S-wave is close to 300, and a sample having a large polarization dependency was produced.
Moreover, in (b), the diffraction efficiency with respect to P-polarized light is about 85%, which shows that the diffraction efficiency is higher than that in the case of (a). On the other hand, the diffraction efficiency for S-polarized light was about 0.2%, and it was confirmed that most components were transmitted. From these results, it can be seen that the ratio of the first-order diffraction efficiency of the P-wave and the S-wave is close to 500, and a sample having a greater polarization dependency than that in (a) can be produced. From these results, as described above, when the polarization state of the laser during the interference exposure is finally made coincident with the direction in which the liquid crystal is aligned, the polarization dependency that occurs in the initial stage is promoted as it is. It has been found that the alignment dependence is more neatly generated, so that the polarization dependence is further increased.

In addition, for sample preparation, if the preparation is performed by performing laser interference exposure while heating above the nematic to isotropic transition temperature (NI point) of the liquid crystal used as the sample, diffraction during production Even if the polarization dependence of efficiency cannot be observed, a large polarization dependence occurs when diffraction efficiency is measured after fabrication, and the shape of the polymer network formed in the liquid crystal layer governs the orientation of the liquid crystal There was found.
Furthermore, even if the prepared sample is once heated to a temperature of the NI point or higher and then subjected to thermal fluctuation to be cooled, the same diffraction efficiency and polarization dependency as the initial stage can be reproduced by returning to the original temperature. Was also confirmed.
The system shown in FIG. 1 makes it possible to clarify the reaction process including the control of the interference exposure time for the production of information recording and display films and the expression of polarization dependence, thereby improving the production efficiency and performance of the sample. It has been found.

(Embodiment 2)
Next, the present invention will be described in Embodiment 2.
In the system shown in FIG. 1, a transparent film of about 10 μm to 100 μm is used as the transparent substrate, and the transparent film is wound up and fixed in a roll shape as shown in Sample 107 (a diagram shown in FIG. 1 surrounded by a dotted line) Then, laser interference exposure was performed in a state where stretching stress was applied.
Changes in reaction time and diffraction intensity at that time are shown in FIG. Here, as the film material, for example, EVOH, TAC, PET, cyclic polyolefin (for example, trade name: ZEONOR manufactured by Nippon Zeon Co., Ltd.), polyethylene, and the like can be used. (A) is a case where the polarization state at the time of laser interference exposure is P-polarized light, and the film is placed in a state where stress is applied so as to substantially coincide with this direction (horizontal direction). On the other hand, (b) shows a case where the polarization state of the laser is S-polarized light, and the film is installed in a state in which stress is applied to the film in a direction (vertical direction) substantially coincident with this. As described above, the film 107 in FIG. 1 is designed so that it can be fixed to a stage made of Peltier elements in any horizontal or vertical direction with respect to the surface plate. The film holding temperature at this time was controlled at 50 ° C. for both (a) and (b).

  From FIG. 11, in (a), the diffraction intensity of the P-polarized light component is large, and the diffraction intensity component of the S-polarized light is hardly generated from the initial process. Further, in (b), the diffraction intensity component of S-polarized light is largely generated, but the diffraction component of P-polarized light is hardly generated. FIG. 12 shows the results of measuring the optical characteristics of these elements using the optical system of FIG. (A) shows that only the diffraction efficiency for P-polarized light is very large, and (b) shows that only the diffraction efficiency for S-polarized light appears very large.

  When the film is heated in a state where stress is applied, the viscosity of the sample is reduced to approximately 3 Pa · s or less and the polarization state of the laser is adjusted to perform interference exposure, the liquid crystal is neatly applied in the direction in which the stress is applied. It can be oriented. As a result, it has been found that an element that exhibits a very large polarization dependency with respect to either P-polarized light or S-polarized light can be produced.

  In the laser interference exposure system shown in FIG. 1, the stage on which the film is fixed is moved while maintaining a fine interval of about several μ while maintaining a narrow beam without expanding the area of the beam emitted from the laser 101, Alternatively, even if laser irradiation is performed using a method such as scanning the laser beam itself, a fine periodic structure corresponding to the laser intensity distribution can be formed. In this case, it is difficult to be affected by noise or the like given to the laser intensity distribution due to disturbances such as vibration, and laser irradiation over a large area is also possible by sequentially scanning the laser beam.

(Embodiment 3)
FIG. 13 shows an example of another embodiment of the method for producing the information recording / displaying film of the present invention. The crimping jig 1301 has a fine periodic structure, one interval of the cycle is about several μm to several tens of μm, the height of the unevenness in the thickness direction is more than twice the periodic interval, and the thickness is It is thicker than the groove spacing. Such a fine periodic structure whose surface irregularities are larger than the groove interval is created by a method such as performing laser interference exposure on a uniformly applied resist material and removing the part other than the hardened part by irradiation with an etching solution. can do.

The thus-formed crimping jig 1301 is heated to about 40 ° C. to 80 ° C. and pressure-bonded to the transparent substrate 1302, thereby applying a stress to the transparent substrate and forming a fine periodic structure and liquid crystal by a thermal polymerization reaction by heating. Are simultaneously performed. In the third embodiment, a transparent film similar to that used in the second embodiment is used as the transparent substrate 1302.
In this step, a thermal polymerization initiator is added to the same sample as used in Embodiment 1, and the pressure bonding jig 1301 is pressed against the transparent film. Since this crimping jig 1301 has a groove depth that is greater than the period of unevenness, as shown in (b), the region on the film sandwiched between adjacent convex surfaces is subjected to tensile stress. For this reason, the transparent substrate 1302 is thermally cured while applying stress. By this thermal layer separation action, the liquid crystal in the transparent substrate 1302 is pushed out from the convex surface of the jig and concentrated on the concave surface. In this part, the polymer network forming the liquid crystal droplets is formed biased in the stress direction, and the alignment of the liquid crystal is aligned in the direction along the shape, so that it is possible to develop polarization dependence based on the alignment of the liquid crystal become. The direction of the stress applied to the film can be arbitrarily changed by adjusting the stress directly applied to the transparent substrate 1302 and the manner of pressure bonding of the jig. For this reason, it becomes possible to arbitrarily control the polarization dependence of P-polarized light or S-polarized light.

  Actually, as a result of producing a film by this method and measuring the optical characteristics, a result almost the same as the value shown in FIG. 12 is obtained, and it is possible to perform the alignment of the liquid crystal simultaneously with the formation of the fine periodic structure. There was found. According to this method, it is not necessary to use an interference exposure technique for producing an information recording / displaying film, and the manufacturing process is simplified. In addition, since an information recording / displaying film can be formed by transferring an uneven pattern on the surface such as the crimping jig 1301, it is very excellent in mass productivity.

(Embodiment 4)
Next, an attempt was made to record pattern information such as characters and images on the sample 107 by using the spatial light modulator 117 in the optical system shown in FIG. The spatial light modulation element 117 is controlled by the computer 118, and an arbitrary pattern produced on the computer can be displayed on the spatial light modulation element 117. As this spatial light modulation element 117, LC2002 manufactured by HoroEye was used. The display screen is 1.3 inches diagonal, is composed of a twisted nematic liquid crystal panel, has 832 × 624 pixels, and can accommodate SVGA video signals. When a video signal is applied, the polarization state of incident light is modulated according to the magnitude of the voltage applied to each pixel. When a polarizing plate is provided on the emission side, intensity modulation is performed in which the amount of transmitted light changes according to the voltage value applied to each pixel.
Further, in the case where the exit-side polarizing plate is not attached, the phase of light passing through each pixel is modulated by applying a voltage in accordance with the change in the refractive index of the liquid crystal molecules in each pixel. As described above, the spatial light modulator 117 can modulate both transmittance and phase.

Next, laser interference exposure is performed in a state in which the letter “T” of the alpha bed is displayed on the display screen of the spatial light modulator 117 in a size almost full of the screen, and the same film as in the second embodiment is used. An attempt was made to prepare Sample 107.
FIG. 14A shows the letter T recorded on the film at this time in an easily understandable model. In the figure, a fine periodic structure having a lattice structure in the vertical direction is formed in the letter T, and the alignment direction of liquid crystal molecules is perpendicular to the lattice. At this time, the polarization state of the laser was set to be P-polarized light, and horizontal stress was applied to the film. Therefore, the P-polarized component was diffracted in the direction of 30 degrees from the character portion of the film. Place this film on the backlight, place the polarizing plate on the film and observe while rotating the direction of this polarizing plate, the brightest image is the film at the position where the transmission axis of the polarizing plate is horizontal It was found to be observed in the direction of approximately 30 degrees from the front of.
Next, (b) shows a case where a character string of 7 characters is recorded on a film and the transmission axis of the polarizing plate is observed from an oblique direction of 30 degrees in the horizontal direction. In this way, it was confirmed that characters could be clearly recorded on the film.
(C) is a case where only the second and sixth A and E characters of the previous character string are recorded while the stress application direction and the laser polarization state are changed by 90 degrees. (C) was observed under the same polarizing plate setting conditions as in (b), but the letters A and E could not be clearly observed. This is because the S-polarized component is diffracted because the direction of the liquid crystal molecules aligned in the fine periodic structure formed in this character is rotated by 90 degrees unlike other characters. As a result, it was confirmed that the diffracted light was cut by the polarizing plate placed on the film and could not be observed as an image.

  As described above, when recording information such as characters, figures, and objects as a hologram pattern on a film, according to the present invention, not only the pattern information corresponding to the interference intensity distribution of the recorded object but also the alignment direction of the liquid crystal. Corresponding information can be newly embedded as an encryption key. In other words, if the film of the present invention and the transmission axis of the polarizing plate are combined in a predetermined specific direction, it is possible to read and decode information of recorded characters and figures. For this reason, the improvement of the security with respect to the recorded information is expectable compared with the thing by the conventional hologram recording.

(Embodiment 5)
FIG. 15 shows an example of a car navigation system. The direction of observing a liquid crystal display for car navigation from the driver's seat is said to be approximately 30 degrees. In addition, since the driver 1502 does not move greatly from the driver's seat during driving, the angle at which the display of the car navigation is viewed hardly changes. For this reason, if the display screen of the liquid crystal display is preferentially presented in the direction of the driver 1502, it is considered that further improvement in light utilization efficiency and visibility can be expected.
FIG. 16 shows an experimental optical system that was used to examine the effect of applying the information recording and display film produced in the present invention for such an application. The green laser 1601 has the same performance as that used in the first embodiment. The emitted light from the green laser 1601 is converted into circularly polarized light using a quarter-wave plate 1602 and converted into parallel light having a diameter of about 40 mmΦ using a collimator 1603 and a lens 1604. Next, the area of the parallel light is adjusted so as to coincide with the display screen of the liquid crystal panel 1606 of about 2 inches diagonally placed behind the light shielding screen.
Subsequently, parallel light is allowed to pass through the liquid crystal panel 1606, and immediately thereafter, a sample 1607 made of an information recording display film manufactured in Embodiment 2 is placed in accordance with the screen of the liquid crystal panel. The transmission axis of the polarizing plate on the output side of the liquid crystal panel is set so that the polarization component that generates diffracted light in the sample 1607 matches. Therefore, the transmitted light emitted from the liquid crystal panel 1606 is preferentially diffracted in a direction corresponding to the periodic structure formed inside by the sample 1607. By detecting the light intensity while moving the photodetector 1608 in a circle around the liquid crystal panel 1606, the viewing angle characteristics of the light intensity generated by the liquid crystal panel 1606 and the sample 1607 can be measured.

FIG. 17 shows this result. It can be confirmed that the distribution of the detected light intensity in the viewing angle direction is greatly different between the case where the sample 1607 in which the fine periodic structure is recorded like a diffractive optical element is installed and the case where only the liquid crystal panel is provided. In the case of only the liquid crystal panel, the light intensity is distributed around 0 degree in the front, but when the sample 1607 is installed on the surface of the liquid crystal panel, the light intensity is distributed around the 30 degree direction of the viewing angle. It was confirmed that the light emission direction from the liquid crystal panel 1606 was greatly modulated.
Next, FIG. 18 shows an information recording display having the same characteristics as previously used, using a color liquid crystal panel 1801 this time, displaying a color logo on this screen based on the above result. 1 shows an experimental system for installing a film sample 1802 and detecting a display pattern with a CCD camera 1803 by changing the observation angle from the screen. FIG. 19 shows this result. FIG. 19A shows an image detected from a 30-degree direction with respect to the liquid crystal panel 1801, and FIG. 19B shows an image detected from the front. Comparing these images, the image (a) detected from the direction of 30 degrees was about three times as bright as the image, and the image was clearly displayed. On the other hand, the image from the front shown in (b) was an unclear image whose brightness was dark and slightly blurred.

The sample 1802 used here modulates the light emission direction by the diffraction action. For this reason, it has dependence on the incident wavelength, and is composed of several wavelengths such as a color image. For light components incident from a wider angle range, the image is likely to be deteriorated due to color shift. However, in the case of using the information recording / displaying film according to the present invention, the above-described deterioration was not so much observed even for such a color image. This is because the diffractive optical characteristic of the film of the present invention shows a high diffraction efficiency in a wide range with respect to the incident angle as shown in FIG. Conceivable.
As described above, by using the information recording display film manufactured in the present invention, the display direction of the image can be efficiently modulated, and the visibility of the liquid crystal display in the car navigation system as shown in FIG. It was found that it can be applied to higher functions such as improvement, higher brightness, and lower power consumption.

The block diagram of the form of one Example for film manufacture for the information recording display of this invention The figure which shows an example of the time change of the diffraction efficiency in the manufacture process of the film for information recording display of this invention The figure which shows an example of the time change of the diffraction efficiency in the manufacture process of the film for information recording display of this invention The figure which shows an example of the temperature characteristic of the viscosity of the sample used for manufacture of the film for information recording display of this invention Explanatory drawing of an example of the time change of the diffraction efficiency in the manufacture process of the film for information recording display of this invention Explanatory drawing of an example of the formation process of the film for information recording display of this invention The figure which shows an example of the reaction time of the formation process of the film for information recording display of this invention The figure which shows an example of the internal structure of the film for information recording displays of this invention The block diagram of the form of one Example for the optical characteristic measurement of the film for information recording display of this invention The figure which shows an example of the diffraction efficiency of the film for information recording display of this invention The figure which shows another example of the time change of the diffraction efficiency in the manufacture process of the film for information recording display of this invention. The figure which shows another example of the diffraction efficiency of the film for information recording displays of this invention The block diagram of the other form of one Example for the film for information recording display of this invention The figure which shows an example of the pattern recorded on the information recording display film of this invention Configuration diagram of an embodiment of an information recording display film of the present invention The block diagram of the form of one Example for the viewing angle characteristic measurement of the film for information recording display of this invention The figure which shows an example of the viewing angle characteristic of the film for information recording display of this invention The block diagram of the form of one Example for the image display using the information recording display film of this invention The figure which shows an example of the display image using the film for information recording displays of this invention Configuration diagram of an example of a conventional hologram production optical system

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Green laser 102 1/2 wavelength plate 103 ND filter 104 Collimator 105 Mirror 106 Half mirror 107 Sample 108, 109 Photosensor 110 Photodetector 111 Polarizing beam splitter 112 GPIB interface board 113, 118 Computer 114 Peltier device 115 Temperature controller 116 He-Ne laser 117 Spatial light modulator 501 P-polarized diffracted light intensity 502 S-polarized diffracted light intensity 601 Laser irradiation intensity distribution 602 Liquid crystal molecules 603 Transparent substrate 604 Photocured polymer layer 605 Liquid crystal layer 606 Aligned liquid crystal layer 801 Polymer layer 802 Liquid crystal layer 803 Polymer network 901 He-Ne laser 902 Polarizing plate 903 Sample 904 Rotating stage 905, 906 Optical sensor 907 Photo detector 1301 Crimping jig 1302 Transparent substrate 1501 Liquid crystal display 1502 Driver 1601 Green laser 1602 1/4 wavelength plate 1603 Collimator 1604 Lens 1605 Shading screen 1606 Liquid crystal panel 1607 Sample 1608 Photo detector 1801 Liquid crystal panel 1802 Sample 1803 CCD camera 1901 Laser 1902 Beam splitters 1903 and 1904 Mirror 1905, 1906 Objective lens 1907 Object 1908 Recording material 1909 Object light 1910 Reference light

Claims (11)

A sample containing liquid crystal and one or more polymerizable substances selected from monomers, oligomers, and polymers is enclosed in a region sandwiched between transparent substrates, and then the viscosity of the sample is controlled to 3 Pa · s or less by the viscosity control means. state is, and of applying a generally tensile along the direction parallel stress against the transparent substrate is, the irradiating light beam having a 3 mW / cm ² is greater than the light intensity comprising a plurality of periodic intensity distribution having light modulating means A method for producing a film for information recording display in which liquid crystal molecules are aligned along a direction of stress applied to the transparent substrate in a region in which the polymerizable material is partially cured. 2. The method for producing a film for information recording display according to claim 1, wherein the tensile stress applied to the transparent substrate is performed by stretching the transparent substrate . It said light modulating means, the production method according to claim 1, wherein the information recording display film which comprises carrying out the transmittance modulation of the light beam. 2. The method for producing a film for information recording display according to claim 1, wherein the light modulating means is performed by phase modulation of a light beam. 2. The method for producing an information recording / displaying film according to claim 1 , wherein the luminous flux has a polarization state substantially perpendicular or horizontal with respect to a periodic direction of the intensity distribution . The method for producing a film for information recording display according to claim 1, wherein the viscosity control means is a temperature change . 6. The method for producing an information recording / displaying film according to claim 1, wherein a direction of stress applied to the transparent substrate is substantially equal to a polarization direction of a light beam to be irradiated . Said sample The method according to claim 1, wherein the information recording display film, which comprises a photopolymerization initiator material and dye. 2. The information recording display according to claim 1 , wherein a region where the polymerizable substance is partially cured by irradiation with a light beam having a plurality of periodic intensity distributions is present in a plurality of islands on the transparent substrate. Film manufacturing method. Manufacturing method of the preceding SL plurality of island-like regions, the information recording display film of claim 9, wherein it has an asymmetric shape which is stretched in the direction of application of stress. An information recording / displaying film formed by the manufacturing method according to claim 1.

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