JPWO2020071221A1 - Image forming device and image forming method - Google Patents

Abstract

Provided are an image forming apparatus and an image forming method capable of more rationally forming an image on a cholesteric liquid crystal layer.
In an image forming apparatus for forming an image in which a first region, a second region, and a third region having different colors are arranged in a mesh pattern on a cholesteric liquid crystal layer, an exposure unit exposes and adjusts the liquid crystal composition. The part adjusts the ratio of each of the first region, the second region, and the third region in each part of the image. The first region is the region where the exposure amount during exposure is larger, the second region is the region where the exposure amount during exposure is smaller, and the third region is at the boundary position between the first region and the second region. It is an area. Further, the adjusting unit has the above ratio according to the set color set for each part of the image based on the correspondence between the parameter set for adjusting the above ratio and the value changing according to the parameter. To adjust.

Description

The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming apparatus and an image forming method for forming an image on a cholesteric liquid crystal layer.

Image forming technology has advanced with the recent development of inkjet printing technology, and the market for decorative products using image forming technology is also expanding. Under such circumstances, in recent years, a technique for forming an image on a cholesteric liquid crystal layer has been developed. According to this technique, it is possible to reproduce highly saturated colors, which is difficult with ordinary ink printing.

Examples of the technique for forming an image on the cholesteric liquid crystal layer include the techniques described in Patent Documents 1 and 2. The techniques described in Patent Documents 1 and 2 are techniques for forming an image composed of dots of three colors of R (red), G (green) and B (blue) on the cholesteric liquid crystal layer.

In the technique described in Patent Document 1, in order to form dots of three RGB colors, the cholesteric liquid crystal compound is irradiated with laser light at an irradiation amount corresponding to each dot color. Specifically, a recording medium made of a cholesteric liquid crystal compound is used, the amount of laser light is controlled by the irradiation amount control means, and the laser light irradiation position (that is, the dot formation position) on the recording medium is controlled by the irradiation position control means. Be controlled. The laser beam is focused by the fθ lens and irradiated to each dot forming position while scanning the recording medium. As a result, the laser light whose amount of light is controlled moves from the upper side to the lower side while scanning back and forth from side to side. As a result, a color image composed of RGB 3-color dots is formed on the recording medium.

In Patent Document 2, laser light sources of each color of RGB are used, and while each laser light source scans, laser light is irradiated using a recording medium of a cholesteric liquid crystal phase. As a result, a multicolor image composed of three RGB colors is formed.

Japanese Unexamined Patent Publication No. 2005-111935 JP-A-2002-268029

However, in the image forming techniques described in Patent Documents 1 and 2, in order to form dots of three RGB colors, the amount of laser light is adjusted for each dot color, or a light source is provided for each dot color. With such a configuration, it takes time and cost to form an image. Therefore, it is desired to form an image on the cholesteric liquid crystal layer by a more rational method, specifically, a simpler and cheaper method.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to solve the following object.
That is, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide an image forming apparatus and an image forming method capable of more rationally forming an image on a cholesteric liquid crystal layer.

In order to achieve the above object, the image forming apparatus of the present invention is an image forming apparatus for forming an image in which the first region, the second region and the third region having different colors are arranged in a mesh pattern on the cholesteric liquid crystal layer. An exposure unit that exposes the liquid crystal composition constituting the cholesteric liquid crystal layer, and an adjustment unit for adjusting the ratio of each of the first region, the second region, and the third region in each portion of the image. The first region is a region having a larger amount of exposure during exposure, the second region is a region having a lower exposure amount during exposure, and the third region is a first region and a second region. It is an area at the boundary position of the area, and the adjustment part is the set color set for each part of the image based on the correspondence between the parameter set for adjusting the ratio and the value that changes according to the parameter. It is characterized in that the ratio is adjusted according to the above.

In the above configuration, the ratio of each of the first region, the second region, and the third region (hereinafter, each region) in each part of the image is adjusted according to the set color of each part of the image, so that the set color is reproduced well. can do. Further, when the first region and the second region in the image are formed, the third region is concomitantly formed accordingly. Therefore, it is not necessary to adjust the exposure conditions for each of the three regions, and it is possible to reduce labor and cost accordingly. This makes it possible to form an image on the cholesteric liquid crystal layer more rationally as compared with the conventional image forming method.

Further, in the above image forming apparatus, the adjusting unit includes a single mask on which a network pattern is formed, and the network pattern has a transmission unit through which light from the exposed unit is transmitted and light from the exposed unit is blocked. It is preferable that the blocking portion is provided, and the parameters are the area ratio of each of the transmitting portion and the blocking portion in the network pattern and the number of lines per unit area in the network pattern.
In the above configuration, since only one mask is used for pattern exposure, it is possible to reduce labor and cost as compared with the case where a plurality of masks are used for image formation.

Further, in the above image forming apparatus, the value is the chromaticity coordinate of the reproduced color reproduced under the ratio, and the correspondence is the change in the chromaticity coordinate of the reproduced color when the area ratio and the number of lines change. The tendency is more preferable.
In the above configuration, the ratio of each region is adjusted based on the change tendency of the chromaticity coordinates of the reproduced color when the area ratio and the number of lines of each of the transmissive portion and the blocking portion in the network pattern change. As a result, it is possible to adjust the ratio of each region based on the above-mentioned change tendency so that the ratio of each region becomes a more appropriate value for reproducing the set color.

Further, in the above image forming apparatus, in the adjusting unit, the transmissive portion and the blocking portion have a mesh pattern according to the area ratio and the number of lines when the chromaticity coordinates of the reproduced color are closest to the chromaticity coordinates of the set color in the changing tendency. It is more preferable to adjust the ratio using the provided mask.
In the above configuration, by using the above mask, it is possible to adjust the ratio of each region so that the ratio of each region becomes a more appropriate value for reproducing the set color.

Further, in the above-mentioned image forming apparatus, the correspondence relationship may be a change tendency when the area ratio changes in 11 steps and the number of lines changes in 8 steps.
With the above configuration, sufficient data regarding the tendency of change in the chromaticity coordinates of the reproduced color can be obtained. This makes it possible to adjust the ratio of each region so that the ratio of each region becomes a more appropriate value for reproducing the set color.

Further, in the above image forming apparatus, when the set color is decomposed into a plurality of representative colors, the network pattern is configured by synthesizing the same number of unit patterns as the plurality of representative colors, and the area ratio in each unit pattern. The number of lines and the number of lines may be determined according to the unit pattern and the corresponding representative color based on the changing tendency.
In the above configuration, the set color is decomposed into a plurality of representative colors, and a unit pattern for reproducing each representative color is produced. Then, the unit patterns of each representative color are combined to produce a net pattern. By such a procedure, a net-like pattern for reproducing the set color can be appropriately produced.

Further, in the above image forming apparatus, the value is a ratio, and the correspondence relationship may be the correspondence relationship between each of the area ratio and the number of lines and the ratio.
In the above configuration, the ratio of each region is adjusted based on the correspondence between the area ratio and the number of lines of each of the transmissive portion and the blocking portion in the network pattern and the ratio of each region. As a result, it is possible to adjust the ratio of each region so that the ratio of each region becomes a more appropriate value for reproducing the set color.

Further, in the above image forming apparatus, the adjusting unit adjusts the ratio by using a mask in which the transmitting portion and the blocking portion are provided in a mesh pattern at the area ratio and the number of lines corresponding to the ratio at which the set color is obtained. You may.
In the above configuration, by using the above mask, it is possible to adjust the ratio of each region so that the ratio of each region becomes a more appropriate value for reproducing the set color.

Further, in the above image forming apparatus, the correspondence relationship may be a correspondence relationship between a combination of 11 kinds of area ratios and 8 kinds of lines and a ratio.
With the above configuration, sufficient data can be obtained regarding the correspondence between the area ratio and the number of lines of each of the transmissive portion and the blocking portion in the network pattern and the ratio of each region. This makes it possible to adjust the ratio of each region so that the ratio of each region becomes a more appropriate value for reproducing the set color.

Further, in the above image forming apparatus, the ratio at which the set color is obtained is calculated based on the distribution of the spectral reflectance of the set color specified for each color of the first region, the second region, and the third region. , More suitable.
In the above configuration, the ratio of each region is adjusted based on the distribution of the spectral reflectance of the set color. This makes it possible to adjust the ratio of each region so that the distribution of the spectral reflectance of the set color can be reproduced.

Further, in the above image forming apparatus, when an image is divided into a plurality of image pieces, the network pattern is configured by arranging the same number of pattern fragments as the plurality of image pieces side by side, and the area ratio in each pattern fragment. And the number of lines may be determined according to the set color set for the pattern fragment and the corresponding image piece based on the correspondence relationship.
In the above configuration, the image is decomposed into a plurality of image pieces, and a pattern fragment for reproducing the set color of each image piece is produced. Then, by arranging the pattern fragments of each image piece side by side, a network pattern for the entire image is produced. By such a procedure, the above-mentioned network pattern can be appropriately produced.

Further, in the above image forming apparatus, it is more preferable that the set color set for the image piece corresponding to the pattern fragment is a color averaged in the image piece.
In the above configuration, since the set color of the image piece is the color averaged in the image piece, the pattern fragment corresponding to the image piece becomes a simpler pattern. As a result, the network pattern can be produced more easily.

Further, in order to solve the above-mentioned problems, the image forming method of the present invention forms an image in which the first region, the second region and the third region having different colors are arranged in a network on the cholesteric liquid crystal layer. In the forming method, the step of exposing the liquid crystal composition constituting the cholesteric liquid crystal layer according to the image and the ratio of each of the first region, the second region and the third region in each part of the image are adjusted. The process is carried out, the first region is a region having a higher exposure amount at the time of exposure, the second region is a region having a lower exposure amount at the time of exposure, and the third region is the first region and the region. It is a region at the boundary position of the second region, and in the process of adjusting the ratio, for each part of the image based on the correspondence between the parameter set for adjusting the ratio and the value that changes according to the parameter. It is characterized in that the ratio is adjusted according to the set set color.
According to the above method, it is possible to form an image on the cholesteric liquid crystal layer more rationally.

According to the present invention, it is possible to provide an image forming apparatus and an image forming method capable of more reasonably forming an image on a cholesteric liquid crystal layer.

It is a figure which shows the basic procedure of forming an image on a cholesteric liquid crystal layer. It is a figure which shows an example of the mask for the pattern exposure processing. It is explanatory drawing about the 1st region, the 2nd region and the 3rd region formed in the cholesteric liquid crystal layer. It is a figure which shows the structure of the image forming apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the image formed on the cholesteric liquid crystal layer. It is a figure which shows an example of the image formation flow. It is a figure which shows the flow of the correspondence relation identification process. It is a figure which shows an example of a sample pattern. It is a figure which shows an example of a sample image. It is explanatory drawing about the change tendency of the chromaticity coordinate of a reproduction color. It is a figure which shows the change tendency of the chromaticity coordinate of the reproduced color when the area ratio and the number of lines of each of a transparent part and a blocking part change. It is an image diagram which shows the flow of the pattern characteristic setting process which concerns on 1st example (the 1). It is an image diagram which shows the flow of the pattern characteristic setting process which concerns on 1st example (the 2). It is explanatory drawing of the procedure for determining a reproduction pattern characteristic. It is a figure which shows the flow of the 2nd specific process. It is a figure which shows an example of a halftone dot image. It is a figure which shows the halftone dot image before the digital filter processing. It is a figure which shows the halftone dot image after the digital filter processing. It is a figure which shows the halftone dot image which the region corresponding to the 3rd region was extracted. It is an image diagram which shows the flow of the pattern characteristic setting process which concerns on 2nd example.

Hereinafter, the image forming apparatus and the image forming method according to the embodiment of the present invention (the present embodiment) will be described in detail with reference to the preferred embodiments shown in the accompanying drawings. It should be noted that the embodiments described below are merely examples for facilitating the understanding of the present invention, and do not limit the present invention. That is, the present invention may be modified or improved from the embodiments described below without departing from the spirit of the present invention. Also, of course, the present invention includes an equivalent thereof.

Further, in the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
Further, in the present specification, "%" and "part" representing the content rate and the amount used are based on mass unless otherwise specified.
Further, in the present specification, "same", "similar" and "same" include an error range generally accepted in the technical field. Further, in the present specification, the terms "all", "all", "whole surface", etc. include not only the case of 100% but also the error range generally accepted in the technical field, for example, 99% or more. It shall include the case where it is 95% or more, or 90% or more.

Further, in the present specification, the "selective reflection wavelength" is defined as the minimum value Tmin (%) of the transmittance of the target object (member), and the half-value transmittance expressed by the following formula: T1 /. It refers to the average value of two wavelengths showing 2 (%).
Formula for calculating half-value transmittance: T1 / 2 = 100- (100-Tmin) / 2

Further, in the present specification, the “image” means an image actually formed on the cholesteric liquid crystal layer, particularly a color image. The digital image (original image) data required for image formation will be referred to as "image information" below.

Further, in the present specification, the "area" is a unit area constituting an image, and specifically, a dot-shaped small area (dot) and an area between dots correspond to each "area". do. The region in the film 51a, which will be described later, is the same region as the region in the image formed on the cholesteric liquid crystal layer.
Further, in the present specification, the "part" of the image means a part when the image is divided into a plurality of parts according to a predetermined rule (for example, dividing by 1 inch), and one or more areas are defined. include. Information on a plurality of pixels (for example, n × n pixels: n is a natural number of 2 or more) in the image information is associated with one portion in the image.

[Basic procedure for forming cholesteric liquid crystal layer and image]
Prior to the description of the image forming apparatus according to the present embodiment, the basic procedure for forming an image on the cholesteric liquid crystal layer and the cholesteric liquid crystal layer will be described.
The cholesteric liquid crystal layer is a layer containing a cholesteric liquid crystal phase and is composed of a liquid crystal composition. The cholesteric liquid crystal layer is preferably a layer in which the cholesteric liquid crystal phase is fixed, but the cholesteric liquid crystal layer is not limited to this, and may not be fixed. Further, when the cholesteric liquid crystal phase is exposed, the length of the spiral pitch of the cholesteric liquid crystal phase changes in the exposed region. Here, the selective reflection wavelength of the cholesteric liquid crystal phase is determined according to the length of the spiral pitch, and the cholesteric liquid crystal phase exhibits a color corresponding to the selective reflection wavelength (strictly, corresponds to the selective reflection wavelength). Reflects colored light).

Next, the basic procedure for forming an image on the cholesteric liquid crystal layer will be described with reference to FIG. FIG. 1 is a diagram showing a basic procedure for forming an image on a cholesteric liquid crystal layer. In order to form an image on the cholesteric liquid crystal layer, as shown in FIG. 1, the following first to fourth steps are carried out in order.

In the first step, a liquid crystal composition containing a polymerizable liquid crystal compound and a photosensitive chiral agent is applied onto the surface of a transparent base material (not shown) made of a plastic film or thin glass, and a film 51a (coating film) is applied. ) Is formed. As a coating method, a known method can be applied. Further, if necessary, a drying treatment may be carried out after applying the liquid crystal composition.
Examples of the plastic used as the material of the transparent base material include cellulose-based polymer, polycarbonate-based polymer, polyester-based polymer, (meth) acrylic polymer, styrene-based polymer, polyolefin-based polymer, vinyl chloride-based polymer, and amide-based polymer. , Iimide-based polymer, sulfone-based polymer, polyether sulfone-based polymer, polyether ether ketone-based polymer, and the like, and among them, polyethylene terephthalate (PET) or (meth) acrylic-based polymer is preferable.
The transparent base material means a transparent base material having substantially no absorption region in the visible light region. Regarding the characteristics of the transparent substrate, the average transmittance in the wavelength range of 380 nm to 780 nm is preferably 80% or more, more preferably 90% or more. The thickness of the transparent base material is not particularly limited, but is preferably 1 to 100 μm, more preferably 2 to 50 μm.

In the second step, the light source S is used to expose the film 51a. The exposure is performed in, for example, two steps, and the pattern exposure process is performed in the first step. In the pattern exposure process, for example, a mask M having a predetermined net pattern is attached to a transparent base material, and the transparent base material is irradiated with light having a wavelength that the photosensitive chiral agent is exposed to through the mask M. At this time, in the film 51a, the unmasked region is irradiated (exposed) with light at a predetermined intensity, and the light is blocked in the masked region.
The mask M may be attached to the surface (back surface) of the transparent base material opposite to the film 51a, in which case light is irradiated from the back side of the transparent base material. On the contrary, the mask M may be attached to the surface of the transparent base material on the same side as the film 51a, in which case the light is irradiated from the front side of the transparent base material.
In the second stage, the entire surface exposure process of irradiating the entire surface of the film 51a with light from the light source S is performed. By the full exposure process, the chiral agent in the region that was not exposed in the pattern exposure process is exposed to light, and a spiral pitch (for example, a spiral pitch in which the selective reflection wavelength is in the wavelength range of blue light) is obtained. The induced force can be adjusted.
The exposed film 51b is formed by the above two-step exposure. In each region of the exposed film 51b, the structure of the photosensitive chiral agent changes according to the exposure amount. However, the exposure is not limited to the case of performing in two steps, and for example, by performing one exposure using a mask or the like having two or more regions showing different transmission spectra, the above-mentioned two-step exposure can be obtained. The exposure will be the same. Further, while performing pattern exposure, the entire surface exposure is omitted, and instead, each part of the film 51a (strictly speaking, the exposed film 51b) is heated so that the selective reflection wavelength is changed by the heat treatment described later. good.

In the third step, the exposed film 51b is heat-treated (aged) using the heating source T to form the heated film 51c. In the heated film 51c, the liquid crystal compound is oriented to form a cholesteric liquid crystal phase. In the heated film 51c, there are a plurality of regions having different exposure amounts. In each of the plurality of regions having different exposure amounts, the length of the spiral pitch of the cholesteric liquid crystal phase differs depending on the exposure amount, and the selective reflection wavelength differs accordingly. The plurality of regions having different selective reflection wavelengths each exhibit a color corresponding to the selective reflection wavelength.

In the fourth step, ultraviolet rays are irradiated from the ultraviolet light source U toward the heated film 51c to cure the heated film 51c (that is, the film in the state of the cholesteric liquid crystal phase). As a result, a layer in which the cholesteric liquid crystal phase is fixed, that is, the cholesteric liquid crystal layer 40 is formed. Then, a colored image formed by arranging a plurality of regions having different selective reflection wavelengths in a mesh pattern is formed on the cholesteric liquid crystal layer 40. Here, "arranged in a net pattern" means arranging dots (dots) in a pattern corresponding to the color tone in order to reproduce an image having a predetermined color tone by the halftone dot technique. Further, "a plurality of regions are arranged in a mesh pattern" means that at least one of the plurality of regions is arranged as a point and the remaining region is arranged in the space between the points.
The curing method is not particularly limited, and a curing method by heating can be used in addition to the curing method by light irradiation.

By carrying out the series of steps described above, the cholesteric liquid crystal layer 40 on which the image is formed can be obtained. The obtained cholesteric liquid crystal layer 40 is transferred to a circularly polarizing plate via, for example, an adhesive layer. The cholesteric liquid crystal layer 40 may be directly formed on the circularly polarizing plate using the circularly polarizing plate as a base material.

Incidentally, when the cholesteric liquid crystal layer 40 is formed without immobilizing the cholesteric liquid crystal phase, the cholesteric liquid crystal layer 40 is formed by carrying out the first to third steps without carrying out the fourth step. The image can be formed on the liquid crystal display. Further, when a liquid crystal compound that can be oriented at room temperature is used, an image may be formed on the cholesteric liquid crystal layer 40 without performing the heat treatment in the third step.

The above basic procedure is a procedure for forming an image on the cholesteric liquid crystal layer when the liquid crystal composition contains a photosensitive chiral agent, but the procedure is not limited to this embodiment, and for example, Japanese Patent Application Laid-Open No. 2009. Other known methods such as the method described in JP-A-300622 can be adopted.

Further, in the above basic procedure, the liquid crystal composition is applied to the surface of the base material to form the film 51a. Here, the coating method is not particularly limited, and examples thereof include a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method. The method for forming the film 51a is not limited to the coating method, and a method other than coating, for example, an inkjet method, a flexographic printing method, a spray coating method, or the like may be used.

Further, in the above basic procedure, the pattern exposure process is performed by mask exposure. Here, as a specific mask exposure method, for example, contact exposure, proxy exposure, projection exposure and the like can be mentioned.

Further, the pattern exposure process may be performed by scanning exposure in which a laser, an electron beam, or the like is used to focus on a predetermined position without a mask and draw directly. Scanning exposure can be performed by applying, for example, a drawing device that draws a desired pattern image or the like by modulation of light. As a typical example of such a drawing device, a predetermined image is formed by scanning a light beam derived from a light beam generating unit onto an object to be scanned via a light beam deflection scanning unit. There is a configured image forming apparatus. In this type of image forming apparatus, at the time of image forming, the light beam derived from the light beam generating unit is modulated in accordance with the image signal (see, for example, Japanese Patent Application Laid-Open No. 7-52453).

Further, on the type in which an image is formed by scanning a laser beam on the object to be scanned attached to the outer peripheral surface of the drum rotating in the main scanning direction in the sub-scanning direction, and on the inner peripheral surface of the cylinder of the drum. An apparatus of the type that forms an image by rotating and scanning a laser beam on the attached object to be scanned (see, for example, Patent No. 2783481) can also be used.

Further, a drawing device for drawing a pattern image or the like with a drawing head can also be used. For example, an exposure apparatus used for manufacturing a semiconductor substrate or a printing plate, which forms a desired pattern image on an exposed surface such as a photosensitive material by an exposure head, can be used. A typical such exposure head is a head provided with a pixel array having a large number of pixels and generating a group of light spots forming a desired pattern image. By operating the exposure head while moving it relative to the exposed surface, a desired pattern image can be formed on the exposed surface.

As the exposure device as described above, for example, the DMD (Digital Micromirror Device) is moved relative to the exposed surface in a predetermined scanning direction, and the DMD memory cell is moved according to the movement in the scanning direction. An exposure device that forms a desired image on an exposed surface by inputting frame data consisting of a large number of drawing point data corresponding to a large number of micromirrors and sequentially forming a group of drawing points corresponding to the DMD micromirror in chronological order. Has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2006-327084).

As the spatial light modulation element provided in the exposure head, a spatial light modulation element other than the above DMD can also be used. The spatial light modulation element may be either a reflective type or a transmissive type. Examples of other spatial light modulators include MEMS (Micro Electro Mechanical Systems) type spatial light modulators (SLMs), optical elements that modulate transmitted light by electro-optical effects (PLZT elements), and Examples thereof include a liquid crystal shutter array such as a liquid crystal light shutter (FLC). MEMS is a general term for microsystems that integrate micro-sized sensors, actuators, and control circuits using micromachining technology based on the manufacturing process of integrated circuits (ICs), and is a MEMS type spatial light modulation element. Means a spatial light modulation element driven by an electromechanical operation using electrostatic force.

Further, a plurality of diffraction grating light valves (GLVs) arranged in a two-dimensional manner can also be used.

<About pattern exposure processing>
In the above-mentioned pattern exposure process, a plurality of regions of the film 51a of the liquid crystal composition are exposed under different exposure conditions. At this time, the exposure may be performed a plurality of times according to each exposure condition. However, from the viewpoint of image formation efficiency, it is more preferable to perform exposure only once using one mask M having two or more regions having different light transmittances from each other. In this case, since only one mask is used, it is possible to reduce the cost and labor as compared with the case where a plurality of masks are used.

(About the mask)
The mask M for pattern exposure processing will be described with reference to FIG. FIG. 2 is a plan view showing an example of the mask M for pattern exposure processing. Further, in FIG. 2, a part of the network pattern Mp is enlarged and shown. In the following description, the "part" in the network pattern Mp corresponds to the "part" in the image, and both "parts" have the same size. Further, the area of each portion in the network pattern Mp corresponds to a unit area.

The mask M is produced by forming (specifically, printing or transferring) a network pattern Mp on a colorless and transparent sheet material such as an OHP (overhead projector) sheet. Each portion of the net-like pattern Mp is provided with a transparent portion Mc in FIG. 2 and a blocking portion Md painted in black in FIG. The transmission unit Mc is a region through which light is transmitted during the pattern exposure process, and the blocking unit Md is a region where light is blocked during the pattern exposure processing.

Further, in each portion of the network pattern Mp, as shown in FIG. 2, one of the transmissive portion Mc and the blocking portion Md is arranged as dots, and the other is arranged between the dots. Incidentally, in the mask M illustrated in FIG. 2, the blocking portion Md is a circular dot, and the transmitting portion Mc is arranged between the dots.

The characteristics (pattern characteristics) of each part of the network pattern Mp are the area ratios of the transmissive portion Mc and the blocking portion Md in each portion of the network pattern Mp, and the line per unit area in each portion of the network pattern Mp. Represented by a number. Here, the "area ratio" is the ratio (%) of the area occupied by each of the transmitting portion Mc and the blocking portion Md to the area of each portion of the network pattern Mp. In the following description, when the term "area ratio" is simply used, the area ratio means the area ratio of the blocking portion Md.

The "number of lines per unit area" is the number of screen lines [unit per inch], which is the one that exists as a dot among the transmissive portion Mc and the blocking portion Md in each portion of the network pattern Mp. Represents the density of the lines that make up the unit length.

By the way, when the film 51a of the liquid crystal composition is subjected to the pattern exposure process using the mask M on which the network pattern Mp is formed, the region overlapping the transmissive portion Mc (that is, the non-mask region) is irradiated with light. , Light is blocked in the region overlapping the blocking portion Md (that is, the mask region). After that, a full exposure process is performed to expose both the masked region and the non-masked region, but the final exposure amount is such that the non-masked region becomes larger and the masked region becomes smaller. When the cholesteric liquid crystal layer 40 is finally formed, the selective reflection wavelength of the non-masked region becomes the wavelength of red light, and the selective reflection wavelength of the masked region becomes the wavelength of blue light. Become. That is, in the image formed on the cholesteric liquid crystal layer 40, the region that was the non-masked region during the pattern exposure process becomes the first region that exhibits red color, and the region that was the masked region during the pattern exposure process exhibits blue color. There are two areas.

Further, in the image formed on the cholesteric liquid crystal layer 40, in the region at the boundary position between the first region and the second region, the selective reflection wavelength is the wavelength region of green light. That is, as shown in FIG. 3, a blur-like region (hereinafter, the third region) appears at the boundary position between the first region and the second region, and the color of the region is green. FIG. 3 is an explanatory diagram of a first region, a second region, and a third region formed on the cholesteric liquid crystal layer 40. The upper figure of FIG. 3 shows a mask on which the band-shaped pattern Mq is formed, and the lower figure shows the cholesteric liquid crystal layer 40 when the pattern exposure process is performed using the mask.

Supplementing with reference to FIG. 3, in the band-shaped pattern Mq, the band-shaped transmitting portion Mc and the strip-shaped blocking portion Md are alternately arranged. When the pattern exposure process is performed through the mask on which the band-shaped pattern Mq is formed, each part of the image finally formed on the cholesteric liquid crystal layer 40 is represented by the first region (indicated by the symbol A1 in FIG. 3). ) And the second region (indicated by the symbol A2 in FIG. 3) are present in stripes. Here, the first region is a region having a larger exposure amount at the time of exposure, and the second region is a region having a smaller exposure amount at the time of exposure. Further, at the boundary position between the first region and the second region, a third region (denoted by the symbol A3 in FIG. 3) exists linearly. In the case shown in FIG. 3, the line width of the third region is about 40 μm, and this line width is determined according to the composition of the liquid crystal composition, the thickness of the mask used at the time of exposure, and the like.

When the first region and the second region are formed in the cholesteric liquid crystal layer as described above, the third region is formed incidentally at the boundary position between the two regions. The image forming apparatus according to the present embodiment utilizes such a phenomenon to form a first region, a second region, and a third region on the cholesteric liquid crystal layer 40 to form an image. Hereinafter, the image forming apparatus according to the present embodiment will be described in detail.

[Configuration example of image forming apparatus]
A configuration example of the image forming apparatus (hereinafter, image forming apparatus 10) according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration example of the image forming apparatus 10.

The image forming apparatus 10 is an apparatus for forming an image of three colors of R (red), G (green), and B (blue) on the cholesteric liquid crystal layer 40. More specifically, the image forming apparatus 10 forms an image in which the red first region, the blue second region, and the green third region are arranged in a mesh pattern on the cholesteric liquid crystal layer 40. The first region, the second region, and the third region may be regions in which the colors (in other words, the selective reflection wavelength) are different from each other, and the color of each region is not particularly limited. Here, the selective reflection wavelength of the first region is the longest (in other words, the light hits the strongest), the selective reflection wavelength of the second region is the shortest (in other words, the light hits the weakest), and the selection of the third region is performed. The reflected wavelength may have an intermediate length. For example, the color of the first region may be yellow, the second region may be purple on the short wave side of yellow, and the color of the third region may be in the range of blue to cyan.

Here, to add to the image formed by the image forming apparatus 10, as shown in FIG. 5, in each part of the image (for example, the image G shown in FIG. 5), of the first region and the second region. One is arranged as dots and the other is arranged between the dots. Further, the third region is arranged linearly along the outer edge of the dot. FIG. 5 is a diagram showing an example of an image. Further, FIG. 5 shows an enlarged part of the image. Incidentally, in the image G illustrated in FIG. 5, the first region (indicated by the symbol A1 in FIG. 5) is a circular dot, and the second region (indicated by the symbol A2 in FIG. 5) is located between the dots. However, the third region (denoted by the symbol A3 in FIG. 5) is arranged in an annular shape along the edge of the dot.

Returning to the description of the configuration of the image forming apparatus 10, as shown in FIG. 4, the image forming apparatus 10 includes a film forming unit 12, an exposure unit 14, an adjusting unit 16, a heating unit 18, an ultraviolet irradiation unit 20, and pattern characteristics. It has a setting unit 22 and a mask manufacturing unit 24.

The film forming portion 12 forms a film 51a of the liquid crystal composition on one surface of the transparent base material. The film forming portion 12 includes, for example, a device for applying a liquid crystal composition such as a spin coater and a wire bar, a device for spraying a liquid crystal composition such as a spray nozzle, and a liquid crystal composition such as an inkjet printer. Equipment that discharges objects can be used.

The exposure unit 14 exposes the film 51a of the liquid crystal composition. More specifically, the exposure unit 14 performs the pattern exposure process in cooperation with the adjustment unit 16, and then performs the entire surface exposure process by the exposure unit 14 alone. In the present embodiment, the mask exposure is performed only once in the pattern exposure process. Incidentally, as the exposure unit 14, an ultra-high pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, a blue laser, a He-Cd (helium cadmium) laser and the like can be used.

The adjusting unit 16 separates the masked region and the non-masked region in the film 51a in the pattern exposure process, increases the exposure amount of the non-masked region, and decreases the exposure amount of the masked region (strictly speaking, the mask). This is for not exposing the area). In other words, the adjusting unit 16 determines the ratio of each of the first region, the second region, and the third region (hereinafter, also referred to as “each region”) in each portion of the image finally formed on the cholesteric liquid crystal layer 40. It is for adjustment. Here, the ratio of each region is the ratio (%) of the area occupied by each region to the area of each portion of the image.

Further, in the present embodiment, the adjusting unit 16 has a single mask M. A network pattern Mp is formed on the mask M, and the network pattern Mp is provided with a transmission unit Mc through which the light from the exposure unit 14 is transmitted and a blocking unit Md that blocks the light from the exposure unit 14. (See Fig. 2).

Then, in the present embodiment, as described above, when the exposure unit 14 cooperates with the adjustment unit 16 to perform the pattern exposure process, the mask exposure is performed once using a single mask M. That is, the adjusting unit 16 adjusts the ratio of each region in each part of the image in one mask exposure. In other words, the pattern characteristics of each portion of the network pattern Mp formed on the mask M are set so that the ratio of each region in each portion of the image is adjusted to a predetermined value.

More specifically, in the present embodiment, the mask M is produced according to the set color set for each part of the image based on the correspondence between the parameter described later and the value that changes according to the parameter. That is, by using the mask M, the adjusting unit 16 can adjust the ratio of each region in each part of the image according to the set color of each part of the image based on the above-mentioned correspondence. The procedure for producing the mask M will be described in detail later.

The adjustment of the exposure amount is not limited to the adjustment using a mask. For example, when pattern exposure is performed by scanning exposure, for example, by controlling the on / off of the light emitted from the exposed portion 14 by a dot generator or the like, light is emitted only to a portion of the film 51a corresponding to the first region. Can be irradiated. According to such a configuration, it is possible to adjust the ratio of each region in each part of the image without using the mask M.

The heating unit 18 heat-treats the film subjected to the pattern exposure treatment (that is, the exposed film 51d) in order to orient the liquid crystal compound (for example, the polymerizable liquid crystal compound) and bring it into the state of the cholesteric liquid crystal phase. Is given. As the heating unit 18, for example, an electric heater and a heater using a heating gas (including steam) as a heat source can be used.
The ultraviolet irradiation unit 20 irradiates the heat-treated film (that is, the heated film 51c) with ultraviolet rays in order to immobilize the cholesteric liquid crystal phase and form the cholesteric liquid crystal layer 40. As the ultraviolet irradiation unit 20, a metal highland lamp, a high-pressure mercury lamp, an ultraviolet LED (Light Emitting Diode), or the like can be used.

The pattern characteristic setting unit 22 sets the pattern characteristics of each portion of the network pattern Mp formed on the mask M of the adjustment unit 16, that is, the area ratios and the number of lines of the transmissive portion Mc and the blocking portion Md in a predetermined setting procedure. Set according to the rules. Specifically, the pattern characteristic setting unit 22 acquires the image information of the original image and analyzes the image information. Based on the result of this analysis, the set color of each part of the image formed on the cholesteric liquid crystal layer 40 is set. The setting of the setting color will be described in detail in a later section.

After that, the pattern characteristic setting unit 22 reads out the correspondence between the parameter and the value that changes according to the parameter from a storage unit (not shown). Here, the "parameter" is a value set for adjusting the ratio of each region in each part of the image formed on the cholesteric liquid crystal layer 40. Specifically, for example, when mask exposure is performed, the area ratios and the number of lines of the transmissive portion Mc and the blocking portion Md in each portion of the network pattern Mp of the mask M to be used correspond to the "parameter". do. Incidentally, only one of the area ratio and the number of lines may be adopted as a parameter.
The "parameters" when scanning exposure is performed include the number of times the light is irradiated (the number of times the light is turned on and off), the area ratio of the part to be irradiated with the light, and the number of lines when the light-irradiated part is regarded as a dot. In addition, light irradiation intensity and the like can be mentioned.

Further, with respect to the "value that changes according to the parameter", the ratio of each region in each part of the image formed on the cholesteric liquid crystal layer 40 corresponds. Further, the chromaticity coordinates of the reproduced color reproduced under the ratio of each region may also correspond to the "value that changes according to the parameter". Here, the "reproduced color" means that each of the red first region, the blue second region, and the green third region is arranged in a mesh pattern at a predetermined ratio to obtain a color tone (from the human eye). It is the color that is reproduced (see). The "chromaticity coordinate" is a chromaticity value specified on the xy-axis color coordinate space (more specifically, the chromaticity diagram).

The pattern characteristic setting unit 22 sets the pattern characteristics of each part of the network pattern Mp according to the set color of each part of the image based on the read correspondence. More specifically, the pattern characteristic setting unit 22 sets each portion of the network pattern Mp so that the ratio of each region in each portion of the image formed on the cholesteric liquid crystal layer 40 becomes a value corresponding to the set color of each portion of the image. Set the pattern characteristics of. At this time, the pattern characteristic setting unit 22 sets the pattern characteristics of each part of the network pattern Mp so that the reproduced color of each part of the image becomes the same color as the set color, for example.

The mask manufacturing unit 24 is composed of, for example, a printing device such as a printer, and forms (for example, prints) a mesh pattern Mp on a colorless and transparent sheet material such as an OHP sheet to manufacture a mask M. More specifically, the mask making unit 24 forms the net pattern Mp so that the pattern characteristics of each part of the net pattern Mp have the pattern characteristics set by the pattern characteristic setting unit 22 to manufacture the mask M.

[Operation example of image forming apparatus]
Next, an operation example of the image forming apparatus 10 having the above-described configuration will be described. Specifically, a series of flows for forming an image on the cholesteric liquid crystal layer 40 using the image forming apparatus 10 (hereinafter referred to as an image forming flow) will be described with reference to FIG. FIG. 6 is a diagram showing an example of an image formation flow.

In the image forming flow, the image forming apparatus 10 applies the image forming method of the present invention to form an image on the cholesteric liquid crystal layer 40. Specifically, each step shown in FIG. 6 is carried out by the image forming apparatus 10.

In the image forming flow, first, the film forming portion 12 of the image forming apparatus 10 carries out a step of forming the film 51a of the liquid crystal composition on one surface of the transparent base material (S001). The film thickness of the coating film is not particularly limited, but is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and 0.5 to 10 μm in that the cholesteric liquid crystal layer 40 is excellent in reflectivity. More preferred.

In the next step, the pattern characteristic setting unit 22 of the image forming apparatus 10 sets the pattern characteristics in each part of the network pattern Mp with respect to the mask M used for the pattern exposure process in the subsequent step (S002). This step S002 will be described in detail later. It should be noted that this step S002 may be carried out at a time before step S001 for forming the film 51a, or may be carried out at the same time.

In the next step, the mask manufacturing unit 24 of the image forming apparatus 10 manufactures the mask M (S003). In this step S003, the mask manufacturing unit 24 forms (prints) a net-like pattern Mp having the pattern characteristics for each part set in step S002 on a colorless and transparent sheet material. The step S003 may be carried out after the end of step S002, and may be carried out at a time before step S001 for forming the film 51a, or may be carried out at the same time.

In the next step, the exposure unit 14 of the image forming apparatus 10 exposes the film 51a (that is, the film-like liquid crystal composition) (S004, S005).

More specifically, the exposure unit 14 performs a pattern exposure process together with the adjustment unit 16 (S004). The pattern exposure process is performed using the single mask M produced in step S003. By using this mask M, the exposure amount becomes larger in the region of each portion of the film 51a that overlaps with the transmissive portion Mc of the network pattern Mp (that is, the non-masked region). On the other hand, in the region overlapping the blocking portion Md (that is, the mask region), the exposure amount becomes smaller, and strictly speaking, light is not irradiated. Here, the region having a larger exposure amount is the first region, and the region having a smaller exposure amount is the second region. Further, the region at the boundary between the first region and the second region is the third region.

Then, in the pattern exposure process, the mask M adjusts each ratio of each region to a predetermined value. That is, step S004 for performing the pattern exposure process corresponds to a step in which the adjusting unit 16 adjusts the ratio of each region in each portion of the image formed on the cholesteric liquid crystal layer 40. Further, the ratio of each region is adjusted according to the set color of each part of the image based on the above-mentioned correspondence relationship.

After the pattern exposure process is performed, the mask M is removed, and the exposure unit 14 performs the entire surface exposure process on the film 51a (S005). Then, by performing the pattern exposure process and the entire surface exposure process, the first region having the selective reflection wavelength of red light and the blue light are selected in each part of the film 51a (strictly speaking, the exposed film 51b). A second region having a reflection wavelength and a third region having a selective reflection wavelength of green light are formed at a predetermined ratio, respectively.

As described above, the pattern exposure process can be performed by scanning exposure without using a mask. When the pattern exposure process is performed by scanning exposure, the exposure conditions may be changed for each region by controlling the on / off of the light source so that only the region to be the first region in the film 51a is exposed. This makes it possible to adjust the ratio of each region in each part of the image.

In the next step, the heating unit 18 of the image forming apparatus 10 heat-treats the exposed film 51b in order to orient the liquid crystal compound to form a cholesteric liquid crystal phase (S006). The liquid crystal phase transition temperature of the liquid crystal composition is preferably 10 to 250 ° C, more preferably 10 to 150 ° C from the viewpoint of manufacturing suitability. Further, as a preferable heating condition, it is desirable to heat at 40 to 100 ° C. (preferably 60 to 100 ° C.) for 0.5 to 5 minutes (preferably 0.5 to 2 minutes).

In the next step, the ultraviolet irradiation unit 20 of the image forming apparatus 10 performs a curing treatment on the heated film 51c in order to immobilize the cholesteric liquid crystal phase and form the cholesteric liquid crystal layer 40 (S007). Specifically, the heated film 51c is irradiated with ultraviolet rays in an environment where the temperature is room temperature in a nitrogen atmosphere or an environment where the temperature is about 60 ° C. in an oxygen atmosphere. No particular limitation is imposed on the irradiation amount of the ultraviolet, preferably about ^{100~800mJ / cm 2, 200mJ / cm} 2 or less being more preferred. The time for irradiating with ultraviolet rays is not particularly limited, but may be appropriately determined from the viewpoint of the strength and productivity of the obtained reflective layer.

Here, in the image formation flow described above, the step of setting the pattern characteristics of each part of the network pattern Mp will be described again with reference to two examples (hereinafter, the first example and the second example). ..

(First example)
In the first example, the pattern characteristics are set for each of the plurality of unit patterns Mt constituting the network pattern Mp, and then the pattern characteristics of the network pattern Mp are set using the plurality of unit patterns Mt. Here, the unit pattern Mt is a color-coded pattern, and the network pattern Mp according to the first example is configured by synthesizing a plurality of unit patterns Mt (see FIG. 13 and the like).

In the first example, prior to setting the pattern characteristics of each unit pattern Mt, the above-mentioned step of specifying the correspondence relationship (hereinafter referred to as the correspondence relationship specifying step) is carried out. In the correspondence relationship specifying step, the correspondence relationship between the pattern characteristics of the network pattern Mp and the values related to each part of the image is specified. Here, the pattern characteristics of the network pattern Mp are the area ratios of the transmissive portion Mc and the blocking portion Md in each portion of the unit pattern Mt constituting the network pattern Mp, and the line per unit area in each portion of the unit pattern Mt. It is a number. The value for each part of the image is the chromaticity coordinate of the reproduced color reproduced under the ratio of each of the first region, the second region, and the third region in each part of the image.

The correspondence relationship identification step proceeds according to the flow shown in FIG. 7, for example. FIG. 7 is a diagram showing a flow of a correspondence relationship specifying process. More specifically, in the correspondence relationship specifying step, first, the sample pattern Ms shown in FIG. 8 is printed on a colorless and transparent sheet material (S011). The sample pattern Ms is a pattern prepared in advance for setting the pattern characteristics of the unit pattern Mt, and is configured by arranging i × j rectangular patches Msp as shown in FIG. Here, i and j are arbitrary natural numbers of 1 or more, but it is preferable that i is 11 and j is 8 as shown in FIG. Incidentally, FIG. 8 is a diagram showing an example of the sample pattern Ms, and a part of the patch Msp is enlarged and shown in the diagram.

Explaining each patch Msp, the size and shape of each patch Msp are uniform among the patches. Further, although the transmissive portion Mc and the blocking portion Md are regularly arranged in each patch Msp, the pattern characteristics in each patch Msp, that is, the area ratio of each of the transmissing portion Mc and the blocking portion Md, and per unit area. The number of lines in is different between patches. In the sample pattern Ms shown in FIG. 8, each patch Msp is uniformly drawn for convenience of illustration.

More specifically, the area ratio in each patch Msp is preferably changed in a plurality of steps, for example, it is preferable that the area ratio is changed in a range of 0 to 100% at 10% intervals, that is, in 11 steps. Incidentally, in FIG. 8, the area ratio of the blocking portion Md is higher as the patch Msp is located above, and the area ratio of the blocking portion Md is lower as the patch Msp is located below (in other words,). The area ratio of the transmissive portion Mc becomes high).

Further, the number of lines per unit area in each patch Msp may be changed in a plurality of steps, for example, 8 steps (for example, 50 lines, 100 lines, 150 lines, 200 lines, 300 lines in the case of the number of lines). It is preferable to change the number by 400, 500, 600, etc.). Incidentally, in FIG. 8, the patch Msp located on the left side has a smaller number of lines, and the patch Msp located on the right side has a larger number of lines.

Next, using the mask M on which the sample pattern Ms shown in FIG. 8 is formed, the sample image Gs shown in FIG. 9 is formed on the cholesteric liquid crystal layer 40 (S012). The sample images Gs are formed according to the basic procedure of image formation described above. FIG. 9 is a diagram showing an example of sample images Gs.

As shown in FIG. 9, the sample image Gs is composed of i × j rectangular patch images Gsp arranged side by side. Each patch image Gsp corresponds to each patch Msp of the sample pattern Ms, and is formed by exposure using the corresponding patch Msp. In each patch image Gsp, each of the first region, the second region, and the third region is formed at a ratio corresponding to the pattern characteristics of the corresponding patch Msp. As a result, each patch image Gsp exhibits a reproduced color according to the ratio of each region. The reproduced color of each patch image Gsp is a single color and differs between patches. In the sample image Gs shown in FIG. 9, for convenience of illustration, the types of reproduced colors of each patch image Gsp are smaller than the types of actual colors.

Next, the chromaticity is measured for the reproduced color of each patch image Gsp (S013). This step S013 is performed by a known colorimetry (chromaticity measurement technique), and for example, the tristimulus value is measured using a tristimulus chromaticity meter or a spectrochromatic chromaticity meter. At this time, the color is measured in consideration of the fact that the reflection characteristics of the cholesteric liquid crystal layer can be exhibited (that is, the intensity of the reflected light increases in the direction near specular reflection) and that the color changes according to the observation angle. It is better to do. Specifically, it is preferable to measure the color in a direction within ± 30 degrees with respect to the direction perpendicular to the patch image Gsp, and to install the illumination within a range of ± 30 degrees.
In this step S013, the measured value of the chromaticity is acquired as the coordinate value (chromaticity coordinate) of the chromaticity coordinate space for each patch image Gsp.

Next, the correspondence relationship between the chromaticity measurement result obtained for each patch image Gsp and the pattern characteristics of the patch Msp corresponding to each patch image Gsp is specified. Specifically, the chromaticity coordinates of the reproduced color of the patch image Gsp when the area ratios of the transmissive portion Mc and the blocking portion Md in each patch Msp and the number of lines per unit area in each patch Msp change. Identify the trend of change (S014).

In order to explain the contents of this step S014 in more detail, in FIG. 8, i patch Msps having the same number of lines in the patch Msp, for example, patch Msps in the column with the symbol R in FIG. Pay attention to it. These patch Msps correspond to the patch images Gsp in the column with the symbol R in FIG. Here, among the patches Msp in the column R in FIG. 8, the patch Msp having the lowest area ratio of the blocking portion Md has a corresponding patch image Gsp (the patch located at the lowermost side in the column R in FIG. 9). The chromaticity measurement value of the reproduced color of the image Gsp) is plotted in the xy color coordinate space. Next, for the patch Msp having the second lowest area ratio, the chromaticity measurement value of the reproduction color of the corresponding patch image Gsp (the second patch image Gsp from the bottom in the column R in FIG. 9) is set to the xy color. Plot in coordinate space.

Hereinafter, in the same manner, the chromaticity measurement values of the reproduced colors of the patch image Gsp corresponding to the patch Msp are plotted in the xy color coordinate space in order from the patch Msp having the lowest area ratio. As a result, a change curve (graph) as shown in FIG. 10 is specified. This change curve corresponds to the change tendency of the chromaticity coordinates of the reproduced color described above. FIG. 10 is an explanatory diagram of a change tendency of the chromaticity coordinates of the reproduced color. In addition to the above change curve, the figure shows the patch Msp corresponding to the two plots in the change curve.

In the change curve shown in FIG. 10, the plot located on the leftmost side shows the chromaticity measurement value of the reproduced color when the area ratio of the blocking portion Md in the patch Msp is the lowest. Further, in the above change curve, the area ratio increases toward the right, and the plot located on the rightmost side shows the chromaticity measurement value of the reproduced color when the area ratio is the highest.

Then, the number of lines in the patch Msp is changed, and the above change curve is repeatedly acquired. As a result, as shown in FIG. 11, j, specifically, 8 change curves (change trends) can be obtained. As described above, in step S014, as the correspondence relationship between the parameter and the value that changes according to the parameter, the change tendency of the chromaticity coordinate of the reproduced color when the area ratio and the number of lines change (specifically, the change). Specify the curve). More strictly, the change tendency when the area ratio changes in 11 steps and the number of lines changes in 8 steps is specified.

FIG. 11 is a diagram showing a change tendency of the chromaticity coordinates of the reproduced color when the area ratio and the number of lines change. In the figure, the patch Msp corresponding to the plot when the area ratios are the same in each of the two different change curves is shown.

Among the change trends (change curves) shown in FIG. 11, the change tendency located at the lowermost side is the change tendency when the number of lines is the smallest. Further, the number of lines increases toward the upper side, and the change tendency located at the uppermost position is the change tendency when the number of lines is the largest.

After the correspondence relationship specifying step described above is completed, the pattern characteristic setting unit 22 of the image forming apparatus 10 determines the correspondence relationship, that is, the net pattern Mp based on the change tendency of the chromaticity coordinates of the reproduced color. Set the pattern characteristics of each part. Specifically, the pattern characteristic setting step is carried out according to the flow shown in FIGS. 12 and 13. 12 and 13 are image diagrams showing the flow of the pattern characteristic setting process according to the first example.

In the pattern characteristic setting step, first, the pattern characteristic setting unit 22 acquires the image information of the original image (hereinafter, the original image FG) and analyzes the image information (S021). By this analysis, the color of each part of the original image FG is specified. Here, the number of colors specified in this step S021 (in other words, colors that can be expressed by image information) is N (for example, 516 or 256).

In the next step, the pattern characteristic setting unit 22 limits the number of colors for the original image FG (S022). The number of colors limitation is a process of reducing the number of colors that can be expressed by posterization (gradation change). Due to this color number limitation, the color of each part of the original image FG becomes a color in which the number of colors is limited. This color with a limited number of colors corresponds to the set color for each part of the image finally formed on the cholesteric liquid crystal layer 40. Further, the color of each part of the original image FG in which the number of colors is limited is composed of colors (representative colors) smaller than the number of colors N before the limitation. In other words, the set color of each part of the image is a color that can be decomposed into a plurality of representative colors.

In the next step, the pattern characteristic setting unit 22 performs image color division processing on the image information in which the number of colors is limited (S023). As shown in FIG. 12, the image color division process is a process of dividing the original image FG2 indicated by the image information with a limited number of colors into a monochromatic image EG for each representative color.

In the next step, the pattern characteristic setting unit 22 calculates the chromaticity coordinates of the representative color corresponding to the monochromatic image EG for each of the monochromatic image EGs for each representative color (S024). As a result, the representative color corresponding to each monochromatic image EG is expressed as the coordinate value of the xy color coordinate space.

In the next step, the pattern characteristic setting unit 22 determines the pattern characteristic (hereinafter, reproduction pattern characteristic) for reproducing the chromaticity coordinates of the color (representative color) of each monochromatic image EG calculated in step S024 (S025). ). In determining the reproduction pattern characteristic, the pattern characteristic setting unit 22 changes the chromaticity coordinate of the reproduction color when the correspondence relationship specified in the correspondence relationship identification step, strictly speaking, the area ratio and the number of lines in the patch Msp changes. See trends. Then, the pattern characteristic setting unit 22 determines the reproduction pattern characteristic based on the above-mentioned change tendency.

Here, a procedure for determining the reproduction pattern characteristics will be specifically described by taking as an example a case of determining the reproduction pattern characteristics for the chromaticity coordinates (x1, y1) of a representative color corresponding to a certain monochromatic image EG. And.

When determining the reproduction pattern characteristics for the chromaticity coordinates (x1, y1), as shown in FIG. 14, the above is described in the xy color coordinate space in which j change trends (change curves) are drawn. Plot the chromaticity coordinates (x1, y1). FIG. 14 is an explanatory diagram of a procedure for determining the reproduction pattern characteristics.

After that, from among the j change tendencies (change curves), one change tendency (hereinafter, specific change tendency Ca) in which the chromaticity coordinates of the reproduced color are closest to the plotted chromaticity coordinates (x1, y1) is specified. .. In the case shown in FIG. 14, the third change tendency from the top corresponds to the specific change tendency Ca. Then, based on the specific change tendency Ca, the area ratio r1 and the number of lines k1 are specified when the chromaticity coordinates of the reproduced color are closest to the plotted chromaticity coordinates (x1, y1) in the specific change tendency Ca. The area ratio r1 and the number of lines k1 specified in this way are the reproduction pattern characteristics for the chromaticity coordinates (x1, y1) of the representative color corresponding to a certain monochromatic image EG.

The reproduction pattern characteristics are determined by the above procedure. The reproduction pattern characteristics are determined for the chromaticity coordinates of each representative color calculated in step S024 (in other words, the same number as the number of monochromatic image EGs divided from the original image FG2).

In the next step, the pattern characteristic setting unit 22 sets the pattern characteristic of the unit pattern Mt for forming each monochrome image EG (S027). In this step S027, the pattern characteristic setting unit 22 specifies a portion (colored portion) of each monochromatic image EG that exhibits the color of the monochromatic image EG. In each monochromatic image EG shown in FIG. 12, the hatched portion and the white portion correspond to the colored portion.

After that, the pattern characteristic setting unit 22 sets the pattern characteristics of the unit pattern Mt corresponding to the colored portion. Specifically, the pattern characteristic setting unit 22 sets the reproduction pattern characteristic determined in step S026 as the pattern characteristic of the unit pattern Mt. That is, the area ratio and the number of lines in the unit pattern Mt are determined according to the representative color corresponding to the unit pattern Mt based on the change tendency shown in FIGS. 11 and 14.

According to the above procedure, the pattern characteristics in the unit pattern Mt are set. The unit pattern Mt exists in the same number as the number of monochromatic image EGs (in other words, the same number as the representative color). Therefore, the pattern characteristics in each portion of the unit pattern Mt are set for each monochromatic image EG as many times as the monochromatic image EG.

In the next step, the pattern characteristic setting unit 22 determines the network pattern Mp by synthesizing the same number of unit patterns Mt as a plurality of representative colors. As a result, the pattern characteristics in each portion of the network pattern Mp, that is, the area ratios of the transmissive portion Mc and the blocking portion Md, and the number of lines per unit area are set (S027).

When the series of steps up to the above are completed, the pattern characteristic setting step is completed. Then, as described above, the net-like pattern Mp having the pattern characteristics set in the pattern characteristic setting step is formed on the colorless and transparent sheet material, and the mask M is produced.

Then, the pattern exposure process is performed through the produced mask M. In the pattern exposure process, the adjusting unit 16 adjusts the ratio of each of the first region, the second region, and the third region in each portion of the image by using the mask M described above. Here, each portion of the network pattern Mp of the mask M is provided with each of the transmission portion Mc and the blocking portion Md at a predetermined area ratio and the number of lines. Here, the predetermined area ratio and the number of lines are defined as the chromaticity coordinates of the reproduced color in the changing tendency shown in FIG. 14 as the set color of each part of the image (strictly speaking, among the plurality of representative colors constituting the set color, the image. It is the area ratio and the number of lines when the closest to the chromaticity coordinates of each part and the corresponding representative color). As a result, the set color of each part of the image is finally reproduced satisfactorily.
In the pattern characteristic setting step according to the first example, as described above, the number of colors is limited for the original image FG, and the original image FG is divided (clustered) into monochromatic image EGs for each representative color. Such a configuration is particularly effective when the resolution of the original image FG is relatively high.

(Second example)
In the second example, the network pattern Mp is divided into a plurality of pattern fragments Mu, the pattern characteristics of each pattern fragment Mu are set, and then the pattern characteristics of the network pattern Mp are set from the plurality of pattern fragments Mu.

Explaining the pattern fragment Mu, in the second example, the image formed on the cholesteric liquid crystal layer 40 is composed of a plurality of image pieces Gt (see FIG. 20). In other words, in the second example, the image is decomposed (fragmented) into a plurality of image pieces Gt. Here, each of the plurality of image pieces Gt corresponds to a part of the image and includes one or more regions. Then, the pattern for forming each image piece Gt corresponds to the pattern fragment Mu. That is, there are as many pattern fragments Mu as there are image pieces Gt. In the second example, the network pattern Mp is configured by arranging the same number of pattern fragments Mu as a plurality of image pieces Gt side by side (see FIG. 20).

In the second example, the step of specifying the correspondence relationship described above is carried out prior to setting the pattern characteristics for each pattern fragment Mu. This process is different in content from the correspondence relationship specifying process of the first example, and will be referred to as a "second specific process" below in order to distinguish it from the correspondence relationship specifying process of the first example.

In the second specific step, the correspondence between the pattern characteristics of the network pattern Mp and the values related to each part of the image is specified. The pattern characteristic of the network pattern Mp is the area ratio of each of the transmission portion Mc and the blocking portion Md in each pattern fragment Mu constituting the network pattern Mp, and the number of lines per unit area in each pattern cross section Mu. The value for each part of the image is the ratio of each of the first region, the second region, and the third region in each part of the image.

The second specific step proceeds according to, for example, the flow shown in FIG. FIG. 15 is a diagram showing the flow of the second specific process. More specifically, in the second specific step, first, a plurality of types of halftone dot image information is generated (S031). The halftone dot image information is image information showing the halftone dot image HG shown in FIG. The halftone dot image HG is a black-and-white two-color image, and is composed of regularly and uniformly arranged dot-like patterns (dots). FIG. 16 is a diagram showing an example of halftone dot image HG.

In generating halftone dot image information, the area ratio and number of dots in the halftone dot image HG, the type of dot shape, and the like are set. Here, it is preferable to set a plurality of dot area ratios, and for example, it is preferable to set them in the range of 0 to 100% at 10% intervals, that is, to set 11 values. Further, it is preferable to set a plurality of lines, for example, set to eight values (for example, 50 lines, 100 lines, 150 lines, 200 lines, 300 lines, 400 lines, 500 lines, 600 lines, etc.). Is good.
The type of dot shape is not particularly limited, but in the following, it will be set to a circular dot.

In the next step, each halftone dot image HG is developed based on each of the plurality of types of halftone dot image information generated in step S031, and specifically, each halftone dot image HG is drawn on a computer (S032). .. Here, the halftone dot image HG will be described again. The halftone dot image HG is an image corresponding to each portion of the net pattern Mp, strictly speaking, the pattern fragment Mu. That is, the area ratio of the dots in the halftone dot image HG set in step S031 corresponds to the area ratio of each of the transmissive portion Mc and the blocking portion Md in the pattern fragment Mu. Further, the number of lines per unit area in the halftone dot image HG set in step S031 corresponds to the number of lines per unit area in the pattern fragment Mu. Therefore, the plurality of types of halftone dot image information generated in step S031 indicate combinations of 11 different area ratios and 8 different number of lines for each of the transmissive portion Mc and the blocking portion Md in the pattern fragment Mu. ..
In the following, the dots in each halftone dot image HG are assumed to correspond to the blocking portion Md in the corresponding pattern fragment Mu, but are not limited to this, and the above dots correspond to the transmitting portion Mc. It may be.

The halftone dot image HG also corresponds to an image formed by using the pattern fragment Mu, that is, an image piece Gt. Specifically, for example, in the halftone dot image HG, the region located between the dots corresponds to the first region in the image piece Gt, and the dots correspond to the second region and are located around the edges of the dots. The area corresponds to the third area. Therefore, the ratio of each region in each image piece Gt can be obtained from each developed halftone dot image HG.

In obtaining the ratio of each region in each image piece Gt from each halftone dot image HG, the developed halftone dot image HG is subjected to digital filter processing (S033). This digital filter processing is a process for identifying a region located around the edge of the dot in the halftone dot image HG, that is, a region corresponding to a third region. The third region has a predetermined width (specifically, a width determined according to the material of the cholesteric liquid crystal layer, the mask used at the time of exposure, and the like) at the boundary position between the first region and the second region. In consideration of this point, when performing the above digital filter processing on the halftone dot image HG, it is preferable to adjust the resolution of the halftone dot image HG so as to be compatible with the digital filter. For easy understanding, the resolution may be adjusted so that the width of the region located around the edge of the dot becomes the above-mentioned predetermined width.

From the implementation of the digital filter processing, the halftone dot image HG shown in FIG. 17 (strictly speaking, the halftone dot image HG whose resolution has been adjusted) is a region having a predetermined width around the edge of the dot as shown in FIG. (That is, the third region) can be converted into the added halftone dot image HG. Note that FIG. 17 shows the halftone dot image HG before the digital filter processing, and FIG. 18 shows the halftone dot image HG after the digital filter processing.

After that, the ratio of each region in the halftone dot image HG is calculated (S034). Specifically, first, the ratio of the region corresponding to the second region in the halftone dot image HG whose resolution has been adjusted in step S033 is calculated. More specifically, the halftone dot image HG shown in FIG. 17 is image-analyzed to calculate the ratio of the area occupied by the dots in the halftone dot image HG.

Secondly, the ratio of the region corresponding to the third region in the halftone dot image HG subjected to the digital filter processing in step S033 is calculated. Specifically, the halftone dot image HG before the digital filter processing shown in FIG. 17 and the halftone dot image HG after the digital filter processing shown in FIG. 18 are based on the halftone dot image HG as shown in FIG. Acquire the point image HG. In the halftone dot image HG illustrated in FIG. 19, only the region arranged around the edge of the dot (that is, the region corresponding to the third region) is extracted and appears as a white annular region. Then, the halftone dot image HG shown in FIG. 19 is analyzed to calculate the ratio of the annular region in the halftone dot image HG.
Note that FIG. 19 is a diagram showing a halftone dot image HG in which a region corresponding to a third region is extracted.

Thirdly, the ratio of the region corresponding to the first region is calculated from the ratio of the regions corresponding to each of the second region and the third region in the halftone dot image HG calculated so far.

By the above procedure, the ratio of each region in the halftone dot image HG can be calculated. Then, the second specific step is completed through a series of steps described above.

Upon completion of the second specific step, the correspondence between the type of halftone dot image information and the ratio of each region in the halftone dot image HG for each type is specified. Here, as described above, the halftone dot image information indicates the area ratio and the number of lines of each of the transmissive portion Mc and the blocking portion Md in the pattern fragment Mu. Further, the ratio of each region in the halftone dot image HG corresponds to the ratio of each region in the image piece Gt. Therefore, the second specific step clarifies the correspondence between the area ratio and the number of lines in each pattern fragment Mu and the ratio of each region in the image piece Gt. More precisely, the correspondence between the combination of 11 area ratios and 8 line numbers set for the pattern fragment Mu and the ratio of each region in the image piece Gt is specified.

After the completion of the second specific step, the pattern characteristic setting unit 22 of the image forming apparatus 10 sets the pattern characteristics of each part of the network pattern Mp based on the above-mentioned correspondence. Specifically, the pattern characteristic setting step is carried out according to the flow shown in FIG. FIG. 20 is an image diagram showing the flow of the pattern characteristic setting process according to the second example.

In the pattern characteristic setting step, first, the pattern characteristic setting unit 22 divides the original image FG into a plurality of image pieces Gt (S041). Here, the plurality of image pieces Gt obtained by dividing the original image FG are synonymous with the plurality of image pieces forming the image finally formed on the cholesteric liquid crystal layer 40.

The original image FG in the second example is a full-color image represented by each gradation of three RGB colors. Therefore, each image piece Gt is also a full-color image. Further, as described above, each image piece Gt corresponds to one of a plurality of pattern fragments Mu constituting the network pattern Mp.

In the next step, the pattern characteristic setting unit 22 performs resolution conversion for each image piece Gt (S042). In this resolution conversion, the color of each image piece Gt is averaged within each image piece Gt. That is, the color of each image piece Gt2 whose resolution has been converted is a single color, and is a color expressed by each gradation of the three RGB colors. The color of each image piece Gt2 whose resolution has been converted corresponds to the set color of each part of the image finally formed on the cholesteric liquid crystal layer 40.

In the next step, the pattern characteristic setting unit 22 performs RGB area ratio conversion on the color of each image piece Gt2 whose resolution has been converted (S043). The RGB area ratio conversion is a process for obtaining the area ratio of each region of RGB3 colors (strictly speaking, the area ratio with respect to the area of the image piece Gt2) necessary for expressing the color of the image piece Gt2 whose resolution has been converted. Is. In the following, the area ratio of the red (R) region will be referred to as the R ratio, the area ratio of the green (G) region will be referred to as the G ratio, and the area ratio of the blue (B) region will be referred to as B. Let's call it rate. Further, the R rate, the G rate and the B rate are collectively referred to as "RGB area ratio".

Here, the procedure of RGB area ratio conversion will be specifically described by taking as an example a case where RGB area ratio conversion is performed on the color of one resolution-converted image piece Gt2 (hereinafter, conversion target color). I will do it.

When performing RGB area ratio conversion on a conversion target color, first, the conversion target color is converted into a chromaticity value (chromaticity coordinate) in the xy color coordinate space. In addition, the RGB spectral reflectance is specified for each chromaticity value. The RGB spectral reflectance is the reflectance of each color of red (R), which is the color of the first region, blue (G), which is the color of the second region, and green (B), which is the third region. Information indicating the distribution of (spectral reflectance).

In order to specify the RGB spectral reflectance of the color to be converted, for example, a plurality of patch images (not shown) having different chromaticity values are formed in advance on the cholesteric liquid crystal layer 40. Then, the RGB spectral reflectance is measured by applying a known measurement method (spectroscopy) to the chromaticity value of each patch image. As a result, the correlation between the chromaticity value and the RGB spectral reflectance becomes clear.

Here, once the RGB area ratio is determined, the RGB spectral reflectance at that time is uniquely determined. In other words, the RGB area ratio is determined according to the RGB spectral reflectance. Further, if the RGB spectral reflectance is determined from the correlation between the chromaticity value and the RGB spectral reflectance, the chromaticity value at that time is uniquely determined. In other words, the RGB spectral reflectance is determined according to the chromaticity value. From the above relationship, it is possible to specify the RGB area ratio for reproducing the conversion target color from the chromaticity value of the conversion target color. In this way, RGB area ratio conversion is performed for the color to be converted.

Here, the RGB area ratio obtained for the color of each image piece Gt2 whose resolution has been converted corresponds to the ratio of each region in each part of the image set so as to obtain the set color of each part of the image. Further, the RGB area ratio is obtained based on the RGB spectral reflectance for the color (that is, the set color) of each image piece Gt2 whose resolution has been converted.

In the next step, the pattern characteristic setting unit 22 sets the pattern characteristics of each pattern fragment Mu according to the RGB area ratio of each image piece Gt2 calculated in step S043 (S044). Specifically, the pattern characteristic setting unit 22 refers to the correspondence relationship specified in the second specific step when determining the pattern characteristic of each pattern fragment Mu. Then, the pattern characteristic setting unit 22 determines the pattern characteristic in each pattern fragment Mu according to the color (set color) of the corresponding image piece Gt2 based on the above-mentioned correspondence relationship.

More specifically, the pattern characteristic setting unit 22 determines the area ratio in the corresponding pattern fragment Mu and the area ratio in the corresponding pattern fragment Mu from the RGB area ratio (ratio) for the color of one resolution-converted image piece Gt2 based on the above correspondence. Determine the number of lines. This process is repeated for each of the resolution-converted image pieces Gt2. As a result, the pattern characteristics are set for each of the same number of pattern fragments Mu as the image piece Gt2.

In the next step, the pattern characteristic setting unit 22 determines the network pattern Mp by arranging the plurality of pattern fragments Mu at corresponding positions and arranging them. As a result, the pattern characteristics in each portion of the network pattern Mp, that is, the area ratios of the transmissive portion Mc and the blocking portion Md in each portion, and the number of lines per unit area in each portion are set (S045).

When the series of steps up to the above are completed, the pattern characteristic setting step is completed. Then, as described above, the net-like pattern Mp having the pattern characteristics set in the pattern characteristic setting step is formed on the colorless and transparent sheet material, and the mask M is produced.

Then, the pattern exposure process is performed through the produced mask M. In the pattern exposure process, the adjusting unit 16 adjusts the ratio of each region in each part of the image by using the mask M described above. Here, each portion of the mesh pattern Mp of the mask M is provided with a transmission portion Mc and a blocking portion Md at an area ratio and a number of lines corresponding to the ratio at which the set color of each portion of the image is obtained. As a result, in each part of the image finally formed on the cholesteric liquid crystal layer 40, the set color of each part is reproduced well.
In the pattern characteristic setting step according to the second example, as described above, the original image FG is divided into a plurality of image pieces Gt, the resolution of each image piece Gt is adjusted, and the color of each image piece Gt is averaged. Make it a single color. Such a configuration is particularly effective when the number of gradations of the original image FG is relatively large.

[About the superiority of the present invention]
As described above, in the image forming apparatus and the image forming method of the present invention, the exposure unit 14 exposes the film 5a of the liquid crystal composition, and the adjusting unit 16 provides the first region in each part of the image. Adjust the ratio of each of the second region and the third region. Here, the first region is a region having a larger exposure amount at the time of exposure, the second region is a region having a smaller exposure amount at the time of exposure, and the third region is a region of the first region and the second region. This is the area that occurs at the boundary position. Then, the adjusting unit 16 adjusts the ratio according to the set color of each part of the image based on the correspondence between the parameter for adjusting the ratio of each region and the value that changes according to the parameter. This makes it possible to form an image on the cholesteric liquid crystal layer 40 more rationally as compared with the conventional image forming method.

More specifically, as described in the section "Background Technology", in recent years, a technique for forming an image on a cholesteric liquid crystal layer has been developed for reasons such as reproducing highly saturated colors. As an example thereof, the techniques described in Patent Document 1 and Patent Document 2 can be mentioned. However, in the image forming techniques described in Patent Documents 1 and 2, in order to form an image composed of dots of three RGB colors, the amount of laser light is adjusted for each dot color, or a light source is provided for each dot color. .. With such a configuration, it takes time and cost to form an image.

On the other hand, in the present invention, as described above, the ratio of each of the three regions in each part of the image is adjusted according to the set color set for each part of the image, so that the set color is reproduced well. can do. Further, when the first region and the second region in the image are formed, the third region is concomitantly formed accordingly. Therefore, in forming the above three regions, it is not necessary to adjust the exposure conditions for each of the three regions, and it is possible to reduce labor and cost accordingly. This makes it possible to form an image on the cholesteric liquid crystal layer 40 in a shorter time with a cheaper configuration as compared with a conventional image forming method.

Further, in the above-described embodiment (the present embodiment), only one mask M is used for adjusting the exposure conditions in the pattern exposure process. Therefore, as compared with the case where a plurality of masks are used for image formation, labor and cost can be reduced. As a result, it becomes possible to form an image on the cholesteric liquid crystal layer 40 more rationally.

[About liquid crystal composition]
Examples of the material used for forming the cholesteric liquid crystal layer include a liquid crystal composition containing a liquid crystal compound. The liquid crystal compound is preferably a liquid crystal compound having a polymerizable group (polymerizable liquid crystal compound).
The liquid crystal composition containing the polymerizable liquid crystal compound may further contain a chiral agent, a polymerization initiator and the like. Hereinafter, each component will be described in detail.

--Polymerized liquid crystal compound ---
The polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, but is preferably a rod-shaped liquid crystal compound.
Examples of the rod-shaped polymerizable liquid crystal compound forming the cholesteric liquid crystal layer include a rod-shaped nematic liquid crystal compound. Examples of rod-shaped nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidins, and alkoxy-substituted phenylpyrimidins. , Phenyldioxans, trans, and alkenylcyclohexylbenzonitriles are preferred. Not only low molecular weight liquid crystal compounds but also high molecular weight liquid crystal compounds can be used.

The polymerizable liquid crystal compound is obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, and an unsaturated polymerizable group is preferable, and an ethylenically unsaturated polymerizable group is more preferable. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups contained in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. Examples of polymerizable liquid crystal compounds include Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, 562,648, 5770107, WO 95/22586. , 95/24455, 97/00600, 98/23580, 98/52905, 1-272551, 6-16616, 7-110469. , No. 11-8801, JP-A-2001-328973, and the like. Two or more kinds of polymerizable liquid crystal compounds may be used in combination. When two or more kinds of polymerizable liquid crystal compounds are used in combination, the orientation temperature can be lowered.

The amount of the polymerizable liquid crystal compound added to the liquid crystal composition is preferably 75 to 99.9% by mass, preferably 80 to 99% by mass, based on the solid content mass (mass excluding the solvent) of the liquid crystal composition. It is more preferably mass%, and even more preferably 85-90 mass%.

--Chiral agent (optically active compound) ---
The chiral agent has the function of inducing the helical structure of the cholesteric liquid crystal phase. Since the chiral compound has a different twisting direction or spiral pitch of the spiral induced by the compound, it may be selected according to the purpose.
The chiral agent is not particularly limited, and is a chiral agent for known compounds (for example, Liquid Crystal Device Handbook, Chapter 3, Section 4-3, TN (twisted nematic), STN (Super-twisted nematic), p. 199, Japanese Studies. (Described in 1989, edited by the 142nd Committee of the Promotion Association), isosorbide, isomannide derivatives can be used.
The chiral agent generally contains an asymmetric carbon atom, but an axial asymmetric compound or a surface asymmetric compound that does not contain an asymmetric carbon atom can also be used as the chiral agent. Examples of axial asymmetric compounds or surface asymmetric compounds include binaphthyl, helicene, paracyclophane and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, the repeating unit derived from the polymerizable liquid crystal compound and the repeating unit derived from the chiral agent are derived by the polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. Polymers with repeating units can be formed. In this aspect, the polymerizable group of the polymerizable chiral agent is preferably a group of the same type as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and preferably an ethylenically unsaturated polymerizable group. More preferred.
Moreover, the chiral agent may be a liquid crystal compound.

As described above, when the magnitude of the spiral pitch of the cholesteric liquid crystal phase (in other words, the reflection wavelength range) is controlled by the exposure amount when forming an image on the cholesteric liquid crystal layer, the cholesteric liquid crystal is sensitive to light. It is preferable to use a chiral agent (hereinafter, also referred to as a photosensitive chiral agent) capable of changing the spiral pitch of the phase.
The photosensitive chiral agent is a compound that can change the structure by absorbing light and change the spiral pitch of the cholesteric liquid crystal phase. As such a compound, a compound that causes at least one of a photoisomerization reaction, a photodimerization reaction, and a photodegradation reaction is preferable.
A compound that causes a photoisomerization reaction is a compound that causes stereoisomerization or structural isomerization by the action of light. Examples of the photoisomerized compound include an azobenzene compound and a spiropyran compound.
Further, the compound that causes a photodimerization reaction means a compound that causes an addition reaction between two groups and cyclizes by irradiation with light. Examples of the photodimerized compound include a cinnamic acid derivative, a coumarin derivative, a chalcone derivative, a benzophenone derivative and the like.

As the photosensitive chiral agent, a chiral agent represented by the following general formula (I) is preferably mentioned. This chiral agent can change the orientation structure such as the spiral pitch (twisting force, spiral twisting angle) of the cholesteric liquid crystal phase according to the amount of light at the time of light irradiation.

In the general formula (I), Ar ¹ and Ar ² represent an aryl group or a heteroaromatic ring group.
The ^{aryl group represented by Ar 1} and Ar ² may have a substituent, and has a total carbon number of 6 to 40, more preferably a total carbon number of 6 to 30. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a hydroxyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a carboxyl group, a cyano group, or a heterocycle. The group is preferable, and a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, a hydroxyl group, an acyloxy group, an alkoxycarbonyl group, or an aryloxycarbonyl group is more preferable.
Another preferred embodiment of the substituent includes a substituent having a polymerizable group. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, and an acryloyl group or a methacryloyl group is preferable.
The substituent having a polymerizable group preferably further contains an arylene group. Examples of the arylene group include a phenylene group.
A preferred embodiment of the substituent having a polymerizable group is a group represented by the formula (A). * Represents the bond position.
Equation (A) * -L ^A1- (Ar) _n- L ^A2- P
Ar represents an arylene group. P represents a polymerizable group.
^LA1 and ^LA2 each independently represent a single bond or a divalent linking group. Examples of the divalent linking group, -O -, - S -, - NR F - (R F represents a hydrogen atom, or an alkyl group.), - CO-, an alkylene group, an arylene group, and, of these Examples include combinations of groups (eg, -O-alkylene group-O-).
n represents 0 or 1.

Among such aryl groups, the aryl group represented by the following general formula (III) or (IV) is preferable.

^{R 1} in the general formula (III) ^{and R 2} in the general formula (IV) are independently hydrogen atom, halogen atom, alkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, alkoxy group, respectively. Represents a hydroxyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a carboxyl group, a cyano group, or a substituent having the above polymerizable group (preferably a group represented by the formula (A)). .. Among them, a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, a hydroxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, or a substituent having the above polymerizable group (preferably, The group represented by the formula (A) is preferable, and the alkoxy group, the hydroxyl group, the acyloxy group, or the substituent having the above-mentioned polymerizable group (preferably the group represented by the formula (A)) is more preferable.
^{L 1} in the general formula (III) ^{and L 2} in the general formula (IV) independently represent a halogen atom, an alkyl group, an alkoxy group, or a hydroxyl group, and have an alkoxy group having 1 to 10 carbon atoms. Alternatively, a hydroxyl group is preferable.
l represents an integer of 0, 1 to 4, and 0 and 1 are preferable. m represents an integer of 0, 1 to 6, and 0 and 1 are preferable. When l and m are 2 or more, L ¹ and L ² may represent different groups.

The ^{heteroaromatic ring group represented by Ar 1} and Ar ² may have a substituent, and has a total carbon number of 4 to 40, more preferably a total carbon number of 4 to 30. As the substituent, for example, a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a hydroxyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, or a cyano group is preferable. A halogen atom, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, or an acyloxy group is more preferable.
Examples of the heteroaromatic ring group include a pyridyl group, a pyrimidinyl group, a frill group, a benzofuranyl group and the like, and among these, a pyridyl group or a pyrimidinyl group is preferable.

The content of the chiral agent in the liquid crystal composition is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%, based on the total molar amount of the polymerizable liquid crystal compound.

--Polymerization initiator ---
When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is allowed to proceed by irradiation with ultraviolet rays, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by irradiation with ultraviolet rays. Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,376,661 and 236,670), acidoin ethers (described in US Pat. No. 2,448,828), and α-hydrogen-substituted fragrances. Group acidoine compounds (described in US Pat. No. 2722512), polynuclear quinone compounds (described in US Pat. Examples thereof include aclysin and phenazine compounds (described in Japanese Patent Application Laid-Open No. 60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (described in US Pat. No. 4,212,970). ..
The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5% by mass to 12% by mass, based on the content of the polymerizable liquid crystal compound.

--Other additives ---
In the liquid crystal composition, if necessary, a surfactant, a cross-linking agent, a polymerization inhibitor, an antioxidant, a horizontal alignment agent, an ultraviolet absorber, a light stabilizer, a coloring material, and metal oxide fine particles are added. Etc. can be added within a range that does not deteriorate the optical performance and the like.

10 Image forming device 12 Film forming part 14 Exposure part 16 Adjustment part 18 Heating part 20 Ultraviolet irradiation part 22 Pattern characteristic setting part 24 Mask making part 40 Cholesteric liquid crystal layer 51a Film 51b Exposed film 51c Heated film Ca Specific change tendency EG Single color Image FG, FG2 Original image G image Gs sample image Gsp patch image Gt, Gt2 Image piece HG halftone dot image M mask Mc transmission part Md blocking part Mp net pattern Mq band pattern Ms sample pattern Msp patch Mt unit pattern Mu pattern fragment S light source T heating source U ultraviolet light source

Claims (13)

An image forming apparatus for forming an image in which a first region, a second region, and a third region having different colors are arranged in a network on a cholesteric liquid crystal layer.
An exposed portion that exposes the liquid crystal composition constituting the cholesteric liquid crystal layer, and an exposed portion.
Each portion of the image has an adjusting portion for adjusting the ratio of each of the first region, the second region, and the third region.
The first region is a region having a larger exposure amount during exposure, the second region is a region having a lower exposure amount during exposure, and the third region is the first region and the second region. The area at the boundary of the area,
The adjusting unit adjusts the ratio according to the set color set for each part of the image based on the correspondence between the parameter set for adjusting the ratio and the value that changes according to the parameter. An image forming apparatus characterized by adjusting. The adjustment unit comprises a single mask on which a reticulated pattern is formed.
The net-like pattern is provided with a transmitting portion through which light from the exposed portion is transmitted and a blocking portion in which light from the exposed portion is blocked.
The image forming apparatus according to claim 1, wherein the parameters are the area ratios of the transmissive portion and the blocking portion in the network pattern, and the number of lines per unit area in the network pattern. The value is the chromaticity coordinate of the reproduced color reproduced under the ratio.
The image forming apparatus according to claim 2, wherein the correspondence is a tendency of change in the chromaticity coordinates of the reproduced color when the area ratio and the number of lines change. In the adjusting unit, each of the transmitting portion and the blocking portion has a net shape based on the area ratio and the number of lines when the chromaticity coordinates of the reproduced color are closest to the chromaticity coordinates of the set color in the changing tendency. The image forming apparatus according to claim 3, wherein the ratio is adjusted by using the mask provided on the pattern. The image forming apparatus according to claim 3 or 4, wherein the correspondence relationship is the change tendency when the area ratio changes in 11 steps and the number of lines changes in 8 steps. When the set color is decomposed into a plurality of representative colors,
The network pattern is composed of synthesizing the same number of unit patterns as the plurality of representative colors.
The image forming apparatus according to claim 5, wherein the area ratio and the number of lines in each of the unit patterns are determined according to the representative color corresponding to the unit pattern based on the changing tendency. The value is the ratio,
The image forming apparatus according to claim 2, wherein the correspondence is a correspondence between each of the area ratio and the number of lines and the ratio. The adjusting unit uses the mask provided in which each of the transmitting portion and the blocking portion has the mesh pattern at the area ratio and the number of lines corresponding to the ratio at which the set color is obtained. The image forming apparatus according to claim 7. The image forming apparatus according to claim 7 or 8, wherein the correspondence is a correspondence between 11 combinations of the area ratio and 8 combinations of the number of lines and the ratio. The ratio from which the set color is obtained is calculated in claim 8 based on the distribution of the spectral reflectance of the set color specified for each color of the first region, the second region and the third region. The image forming apparatus described. When the image is divided into a plurality of image pieces,
The network pattern is configured by arranging the same number of pattern fragments as the plurality of image pieces side by side.
The 8 or 9 claim, wherein the area ratio and the number of lines in each of the pattern fragments are determined according to the set color set for the image piece corresponding to the pattern fragment based on the correspondence relationship. Image forming device. The image forming apparatus according to claim 11, wherein the set color set for the image piece corresponding to the pattern fragment is a color averaged in the image piece. An image forming method for forming an image in which a first region, a second region, and a third region having different colors are arranged in a network on a cholesteric liquid crystal layer.
A step of exposing the liquid crystal composition constituting the cholesteric liquid crystal layer and
A step of adjusting the ratio of each of the first region, the second region, and the third region in each part of the image is carried out.
The first region is a region having a larger exposure amount during exposure, the second region is a region having a lower exposure amount during exposure, and the third region is the first region and the second region. The area at the boundary of the area,
In the step of adjusting the ratio, based on the correspondence between the parameter set for adjusting the ratio and the value changing according to the parameter, according to the set color set for each part of the image. An image forming method characterized by adjusting the ratio.

Images