JP4900592B2 - Optical element manufacturing method - Google Patents

Description

The present invention relates to a method of liquid phase region causes a phase difference when light is incident to manufacture an optical element formed by patterning in arbitrary shape.

  In recent years, with the miniaturization of liquid crystal display devices, liquid crystal display devices have come to be widely used in mobile phones, PDAs and the like. In such a small liquid crystal display device, in addition to power saving, high brightness and high contrast are important issues. From this point of view, development of reflective or transflective liquid crystal display devices for power saving and optical elements for improving the brightness and contrast of these liquid crystal display devices have been developed.

As this type of transflective liquid crystal display device, for example, the one described in Patent Document 1 below is known.
1 and 2 are cross-sectional schematic views of a transflective liquid crystal display device (hereinafter abbreviated as a liquid crystal display device unless otherwise specified) 30 described in Patent Document 1 below. These can be cited as an example of a liquid crystal display device to which the optical element 1 of the present invention is suitably applied.

First, the basic configuration of the liquid crystal display device 30 will be described.
The liquid crystal display device 30 includes a semi-transmissive and semi-reflective layer 24, and a reflective display region 17 in which visible light incident from the viewer side (upper side in the figure) is reflected by the reflective portion 24a of the same layer and visually recognized by the viewer; A transmissive display region 16 is formed in which visible light emitted from a backlight 20 provided on the back side (lower side in the drawing) passes through an opening 24b in the same layer and reaches an observer. .
The semi-transmissive / semi-reflective layer 24 is formed by patterning fine openings in a reflective film made of a highly reflective metal film such as aluminum, silver, or an alloy thereof, so that the reflective portion 24a and the open portion 24b are provided for each pixel. In general, it is formed.

In a liquid crystal cell 23 in which various stacks including the driving liquid crystal layer 13 in which the driving liquid crystal molecules 28 are aligned are sandwiched between a pair of glass substrates 11 and 18, driving liquid crystal molecules such as TN (Twisted Nematic) liquid crystal. By driving voltage 28 by applying a voltage, the amount of phase difference given to visible light passing therethrough is changed, and switching between bright display and dark display is performed for each pixel.
Specifically, in the case of the liquid crystal display device 30 shown in FIGS. 1 and 2, the thickness of the driving liquid crystal layer 13 in the transmissive display region 16 is arranged by patterning the optically isotropic gap control layer 25 in the reflective display region 17. The thickness of the reflective display region 17 is twice that of the reflective display region 17. The visible light transmitted through the reflective display region 17 has a half wavelength in the transmissive display region 16 and a quarter wavelength in the reflective display region 17 when no voltage is applied. Designed to give a phase difference. Further, when the voltage is applied, the driving liquid crystal molecules 28 are driven and both of the phase differences given to the transmitted light become zero, so that the transmitted light passes through the linear polarizing plate 10 toward the observer and is visually recognized by the observer. The bright display is switched to the dark display that is absorbed and cannot reach the observer.

In the liquid crystal cell 23, on the inner side (in-cell side) between the glass substrates, first, on the inner surface side of the glass substrate 18 on the back side, a semi-transmissive / semi-reflective layer 24, indium tin oxide (hereinafter abbreviated as ITO), etc. A transparent electrode layer 14b made of a transparent conductive film is laminated, and an alignment film (not shown) for aligning the driving liquid crystal molecules 28 in a desired manner is formed so as to cover the transparent electrode layer 14b. The alignment film is obtained by, for example, rubbing a polyimide layer coated on the transparent electrode layer 14b.
On the other hand, on the inner surface side of the glass substrate 11 on the viewer side, an effective display region and each pixel are partitioned by a light-shielding black matrix (BM) 29.
On the BM 29, colored areas of different colors such as R (red), G (green), and B (blue) are finely arranged with a pixel width so as to fill the effective display area, and the transmitted light is dispersed for each color. A colored layer 12, a transparent electrode layer 14a made of a transparent conductive film such as ITO, and the like are laminated. An alignment film (not shown) for aligning the drive liquid crystal molecules 28 in a desired manner is formed so as to cover the transparent electrode layer 14a.

  On the outside (out-cell side) of the liquid crystal cell 23, the linear polarizing plate 10 is disposed on the viewer side of the glass substrate 11, and the linear polarizing plate 19 is also provided on the back side from the glass substrate 18.

  The liquid crystal display device 30 shown in FIGS. 1 and 2 includes a phase difference control layer 15 for giving a phase difference of ¼ wavelength to visible light incident on the reflective display region 17 from the observer side. Both are prepared. In the liquid crystal display device 30 shown in FIG. 1, the phase difference control layer 15 is on the observer-side glass substrate 11 and between the colored layer 12 and the transparent electrode layer 14a. In the liquid crystal display device 30 shown in FIG. On the side glass substrate 18, it is provided between the transparent electrode layer 14 b and the transflective layer 24.

  The phase difference control layer 15 is formed by patterning a liquid crystal phase region 15a that causes a phase difference in transmitted light and an optically isotropic region 15b that does not cause a phase difference in transmitted light. The liquid crystal phase region 15a and the reflective display region 17 are made to face each other, and the optically isotropic region 15b and the transmissive display region 16 are made to face each other, so that visible light passing through the reflective display region 17 has a desired (¼ wavelength). Phase difference). That is, in the liquid crystal display device 30 shown in FIG. 1, the glass substrate 11 on the viewer side provided with the phase difference control layer 15 gives an optical phase difference of ¼ wavelength with respect to visible light passing through the reflective display region 17. It functions as the element 1. 2, an optical element in which the glass substrate 18 on the back side provided with the phase difference control layer 15 gives a phase difference of ¼ wavelength with respect to visible light passing through the reflective display region 17. Functions as 1.

  Further, in Patent Document 1 below, the phase difference control layer 15 is formed by applying a coating liquid containing polymerizable liquid crystal molecules onto the glass substrate 11 or 18 via (1) the colored layer 12 or the semi-transmissive / semi-reflective layer 24. (2) This is heated to a liquid crystal phase state to align liquid crystal molecules in a desired direction such as homogeneous (horizontal) alignment, and (3) reflective display region 17 ( By irradiating actinic radiation such as ultraviolet rays through a photomask opened corresponding to the reflecting portion 24a), the liquid crystal molecules existing in the region are polymerized and cured in an aligned state, and (4) cured liquid crystal molecules And unpolymerized liquid crystal molecules are both heated to an isotropic phase temperature to transfer only the unpolymerized liquid crystal molecules to the isotropic phase, and (5) the entire liquid crystal molecules are baked to form a photocured liquid crystal phase state. Liquid crystal phase region consisting of liquid crystal molecules and photocuring It has been produced together immobilized and optically isotropic region consisting of the liquid crystal molecules of the isotropic phase state did.

Japanese Patent Application Laid-Open No. 2006-276697

However, in the method of manufacturing the retardation control layer described in Patent Document 1, sufficient resolution cannot be obtained in patterning the liquid crystal phase region 15a and the optically isotropic region 15b in the irradiation of actinic radiation through a photomask. There was a problem.
That is, for the visible light passing through the phase difference control layer 15, a predetermined amount of phase difference (1/4 wavelength) is ideally given in the liquid crystal phase region 15a, and in the optical isotropic region 15b. It is preferable that no phase difference is given. However, in the case of the conventional manufacturing method, an intermediate phase difference less than the predetermined amount is given to the boundary between the liquid crystal phase region 15a and the optically isotropic region 15b. A boundary region that is widened is formed.

When the boundary region is formed so as to reach the reflective display region 17, the visible light that passes through the boundary region cannot obtain a phase difference amount (for example, ¼ wavelength) that should be originally obtained in the liquid crystal phase region 15 a. , The ratio of passing through the linearly polarizing plate 10 is reduced and the amount of light is insufficient. In the dark display, the linearly polarizing plate 10 cannot absorb light appropriately, and thus light leakage occurs. Decrease and color shift occur.
The same applies to the case where the boundary area is formed so as to reach the transmissive display area 16. The visible light that passes through the transmissive display area 16 is not originally provided with a phase difference. However, the visible light that has passed through the boundary area has a phase difference shift. Causes light leakage.

The present invention has been made in order to solve the above-described problems, that is, to provide a method for manufacturing an optical element capable of realizing a liquid crystal phase region that imparts a desired phase difference in a phase difference control layer with high resolution. For the purpose.

The method for producing an optical element according to the present invention includes:
(1) A method for producing an optical element in which a liquid crystal phase region that causes a phase difference in transmitted light is patterned on a light-transmitting substrate,
(I) an application step of applying a coating liquid containing polymerizable liquid crystal molecules and a photopolymerization initiator on the substrate to form a coating film;
(Ii) an alignment step of aligning the liquid crystal molecules in a liquid crystal phase state;
(Iii) A light irradiation step of patterning the liquid crystal phase region by polymerizing and curing the irradiated liquid crystal molecules by irradiating the liquid crystal molecules in the liquid crystal phase state with actinic radiation through a photomask.
Including, and
The wavelength of the light substantially contained active radiation pattern irradiated by the light irradiation step, rather long than the maximum absorption wavelength of the photopolymerization initiator,
The absorbance of the photopolymerization initiator with respect to the light having the shortest wavelength substantially contained in the active radiation irradiated with the pattern is 50% or less of the absorbance with respect to the light having the maximum absorption wavelength. Device manufacturing method;
(2) The method according to (1) above, for producing an optical element in which an isotropic phase region that does not cause a phase difference in transmitted light is patterned on the base material together with the liquid crystal phase region,
After the light irradiation step (iii),
(Iv-1) an isotropic phase transition step for heating the coating film in which the liquid crystal phase region is patterned to bring uncured liquid crystal molecules into an isotropic phase; and (v) liquid crystal molecules in the isotropic phase. A firing step for forming the isotropic phase region by thermally polymerizing each other;
A method for producing an optical element, comprising:
(3) After the light irradiation step (iii),
(Iv-2) A method for producing an optical element according to (1) above, wherein a removal step of removing uncured liquid crystal molecules from the coating film in which the liquid crystal phase region is patterned is performed;
(4) The method for producing an optical element according to any one of (1 ) to (3) , wherein the coating liquid further comprises a thermal polymerization initiator;
Is the gist.

In the present invention, the “liquid crystal phase” means a state in which the liquid crystal molecules are oriented in a certain direction, and is not limited to a state in which the liquid crystal molecules have fluidity such as a liquid, but the liquid crystal molecules are polymerized to each other in an aligned state. Including the fixed state.
The “isotropic phase” means a state in which the orientation of the liquid crystal molecules is not regular, and does not require mathematical strictness in the random orientation of the liquid crystal molecules. Similarly, the fact that the isotropic phase region does not cause a phase difference in the transmitted light is significant for visible light transmitted through the isotropic phase region in a state sandwiched between a pair of linear polarizing plates combined with crossed Nicols. This means a state in which no light leakage is visible to the observer.
In addition to the above isotropic phase region, the “optically isotropic region” is composed of an optically isotropic and light-transmitting resin material such as an acrylic resin, and a gas phase such as air, and the same as above. In addition, it is a region where a state in which no significant light leakage is visible to the observer through visible light passing through the pair of linear polarizing plates combined with crossed Nicols is realized.
“Actinic radiation” means electromagnetic waves and particle beams having high energy such as ultraviolet rays and ionizing radiation.
In addition, the formation of a layer “on the substrate” means that the layer is formed directly in contact with one surface of the substrate or indirectly through another layer. Yes, it does not ask whether the vertical positional relationship between the base material and the layer is the vertical, horizontal, or horizontal direction with respect to the direction of gravity.
Moreover, "substantially cut" light of a predetermined wavelength from the active radiation irradiated with the pattern means that the light of the wavelength included in the active radiation after the cut does not contribute to the photopolymerization of liquid crystal molecules, Specifically, it means that the irradiation intensity of the wavelength light is reduced to 20% or less by cutting. Similarly, the light “substantially included” in the pattern irradiation actinic radiation means light that contributes to the photopolymerization of liquid crystal molecules, specifically, the most irradiation included in the pattern irradiation actinic radiation. When the intensity of light having high intensity is 1, it means light having a wavelength having an irradiation intensity exceeding 0.06.
In addition, “the width of the boundary region that substantially causes a transmitted light to have a phase difference of less than a predetermined amount” means that an optical element sandwiched between linearly polarizing plates in a crossed Nicol state and in a bright display position is observed with a polarizing microscope. Furthermore, it means the width of a region where the transmitted light is significantly observed visually and the transmitted light intensity is significantly observed to be visually inferior to the transmitted light intensity observed in the liquid crystal phase region.

  According to the method for manufacturing an optical element according to the present invention, the liquid crystal phase region and the optically isotropic region patterned in the phase difference control layer can be formed with high resolution, and the width of the boundary region between them can be reduced. Therefore, by using the optical element obtained by such a manufacturing method in a transflective liquid crystal display device, desired bright display and dark display can be performed in the transmissive display area 16 and the reflective display area 17, and the contrast ratio is increased. Therefore, a liquid crystal display device with high optical performance that is high and does not cause color shift can be obtained.

  The optical element of the present invention has a light-transmitting base material having a phase difference control layer in which a liquid crystal phase region that causes a phase difference in transmitted light and an optically isotropic region that does not cause a phase difference in transmitted light are patterned. Laminated on top. In addition, the optical element of the present invention may optionally include other laminated layers such as a colored layer, an alignment film, and a transparent electrode layer. By providing each layer described below, the optical element of the present invention can be used as a color filter of a transflective liquid crystal display device, but in addition, a transmissive or reflective liquid crystal display device, It can also be used in combination with an optical device such as a digital camera that controls the phase difference between the outgoing and incident light.

[About optical element manufacturing method]
The optical element and the method for manufacturing the same according to the present invention can obtain the liquid crystal phase region and the optically isotropic region of the retardation control layer with high resolution. Such optically isotropic regions can be broadly divided into (a) a case where an optically isotropic and light-transmitting material is fixed, and (b) a case where the material is not fixed and optically isotropic by a gas phase such as air. There are two possible cases for obtaining sex. In the case of the former (a), (a-1) an isotropic phase region in which polymerizable liquid crystal molecules are polymerized with each other in an isotropic phase transition state, and (a-2) optical isotropy are provided. And fixing a non-liquid crystalline resin material having a property of polymerization.

3 is a schematic diagram showing a method for manufacturing the optical element 1 according to the first case (a), specifically, the case (a-1). As shown in FIG. 5 (5), a phase difference control layer 15 in which a liquid crystal phase region 15a and an isotropic phase region 15c as an optical isotropic region 15b are patterned and fixed on a substrate 2 is provided. The optical element 1 is produced by forming.
4 is a schematic view showing a method for manufacturing the optical element 1 according to the second case (b). As shown in FIG. 4 (4), the liquid crystal phase region 15a is patterned and fixed on the substrate 2, and a phase difference control in which a gas phase region 15d as an optically isotropic region 15b is disposed therebetween. The optical element 1 is manufactured by forming the layer 15.
Among both manufacturing methods, (1) to (3) in FIGS. 3 and 4 are common steps, and materials used for both manufacturing methods are also common. Specific materials that are suitably used for the production of the optical element of the present invention will be described in detail later.

(I) Coating step As shown in each of FIGS. 3 and 4 (1), a coating liquid containing polymerizable liquid crystal molecules is directly or indirectly applied onto a light-transmitting substrate 2 having orientation ability. Thus, the coating film 4 is formed. The coating liquid is obtained by dissolving the liquid crystal molecules in a solvent and mixing various additives.
As a coating method, a known technique can be used. Specifically, the coating liquid can be applied onto the substrate 2 by a roll coating method, a gravure coating method, a slide coating method, a spin coating method, a dipping method, an ink jet method, or the like.
In order to provide the substrate 2 with an alignment ability, an alignment film 3 for aligning liquid crystal molecules in a desired direction may be formed on the coated surface. For example, when the alignment film 3 is a horizontal alignment film, it can be obtained by applying a polyimide resin material to the base material 2 and then rubbing it in a predetermined direction. When the liquid crystal molecules are vertically aligned (homeotropic alignment), a well-known vertical alignment film is formed as the alignment film 3 and the wettability of the surface of the base material 2 is improved by UV-ozone cleaning treatment or the like. It is also suitable to assist the vertical alignment.

(Ii) Alignment Step Next, the coating film 4 formed on the substrate 2 is dried under reduced pressure to reduce the solvent, and the liquid crystal molecules are held at a predetermined temperature (liquid crystal phase temperature) at which a liquid crystal structure is developed. Is oriented. The alignment of the liquid crystal molecules may be any of horizontal alignment, vertical alignment, twist alignment, bend alignment, hybrid alignment, and the like. However, when the optical element 1 of the present invention is used as a display-side substrate of a transflective liquid crystal display device and the phase difference control layer 15 gives a phase difference of ¼ wavelength to visible light, liquid crystal molecules are horizontally aligned. Good.

(Iii) Light irradiation step From the state of FIGS. 3 and 4 (1) in which the entire liquid crystal molecules contained in the coating film 4 are aligned in a desired direction to form a liquid crystal phase, photo as shown in FIG. The pattern is irradiated with actinic radiation through the mask 5. The light-shielding photomask 5 is provided with an opening 5a corresponding to a position that later becomes the liquid crystal phase region 15a, and only liquid crystal molecules existing in the region are polymerized and cured by exposure to actinic radiation. Can do.
The mask pattern of the photomask 5 is not particularly limited. In the present embodiment, the striped mask pattern is formed so that the strip-like liquid crystal phase region 15a and the optically isotropic region 15b extending in the depth direction of the paper surface are repeated side by side.

In this way, by exposing the liquid crystal molecules in the liquid crystal phase state with actinic radiation to polymerize each other, the liquid crystal phase region 15a is patterned and fixed while maintaining the liquid crystal phase state as shown in each figure (3). Can be
The amount of exposure is preferably about 50 to 500 mJ / cm ² depending on the type of liquid crystal molecules.

  A photopolymerization initiator may be added to the coating liquid together with polymerizable liquid crystal molecules. The photopolymerization initiator can absorb one or a plurality of specific wavelengths of active radiation to generate free radicals, and can three-dimensionally crosslink liquid crystal molecules by radical chain reaction. Thereby, the liquid crystal molecules present in the exposure region of the active radiation can be photopolymerized with each other whether or not the polymerizable liquid crystal molecules used in the present invention have photopolymerizability.

  Further, in the coating film 4, the unexposed area 6 which is shielded by the photomask 5 and is not irradiated with the active radiation remains as the coating film 4, and the liquid crystal molecules existing in the area remain uncured. Phase transition and etching removal are possible.

In the present embodiment, a so-called negative photolithography method in which liquid crystal molecules are polymerized and cured by exposure to actinic radiation has been described as an example. However, the present invention is not limited to this, and a so-called positive photolithography method is used. It may be used. Specifically, the coating film 4 is formed with a coating liquid containing a thermopolymerizable liquid crystal molecule such as an epoxy type, dried and oriented under reduced pressure, and then the whole is heated to temporarily polymerize and cure the liquid crystal molecules. The phase film is further coated with a positive photoresist on the entire surface, and then actinic radiation is pattern-exposed through a photomask having an opening corresponding to the optically isotropic region 15b. Of these, the region may be exposed and removed, and the liquid crystal molecules may be removed from the optically isotropic region 15b by dry etching or the like.
In the following description, a case of using a negative photolithography method will be described as an example. However, those skilled in the art can easily apply a case of performing this in a positive type.

Here, according to the method for manufacturing an optical element according to the present invention, the liquid crystal phase region 15a and the optically isotropic region 15b can be patterned with high resolution.
In the present invention, this is realized by limiting the wavelength of the actinic radiation for pattern exposure.
In the conventional method for producing an optical element exemplified in Patent Document 1, it is general to use ultraviolet rays of 200 to 450 nm widely. According to the knowledge of the present inventors, the following reasons are given. Specifically, it has been clarified that the resolution of the liquid crystal phase region 15a by the photolithography method can be significantly increased by substantially limiting the active radiation to a wavelength exceeding 313 nm, preferably to a wavelength of 320 nm or more. .
The upper limit wavelength of the actinic radiation is not particularly limited. From the viewpoint of having photons with sufficient energy to cause photopolymerization in liquid crystal molecules, light up to about 450 nm is suitable as in the conventional case. Can be used. In addition, it does not exclude that light having a wavelength longer than this is mixed with the active radiation irradiated in the process.
In the present invention for increasing the resolution of the liquid crystal phase region, light having an irradiation intensity as low as not substantially contributing to photopolymerization of liquid crystal molecules must not be excluded from the active radiation for pattern exposure. Therefore, in the following description, when it is expressed that the irradiation light is limited to light of a predetermined wavelength or more, or the short wavelength cut filter is used to cut the short wavelength light of the predetermined wavelength or less, the short wavelength light of the predetermined wavelength or less is used. In addition to the case of cutting completely, the state of cutting this substantially is included.

  The short wavelength actinic radiation is a boundary that gives transmitted light a phase difference less than the liquid crystal phase region 15a between the liquid crystal phase region 15a and the optically isotropic region 15b for the following reasons (a) to (c). Form a region. When the boundary region exceeds 3 μm, when the optical element 1 is applied to a liquid crystal display device, color shift and light leakage due to a phase difference of visible light transmitted through the boundary region are observed by human eyes. As a result, according to the present invention capable of improving the resolution of the phase difference phase region, the width of the boundary region is reduced, and the occurrence of the above problem can be suppressed.

(A) Short-wavelength active radiation is highly scattered and, as shown in FIG. 5A, easily enters the coating film 4 obliquely after passing through the opening 5a of the photomask 5, so that the liquid crystal molecules The photocured region of the taper is widened toward the end. Therefore, the border region of width W ₁ between the unexposed region 6 is formed later becomes optically isotropic region 15b.
The taper can be reduced by bringing the photomask 5 and the coating film 4 into contact with each other for exposure, but since the coating film 4 is exposed in an uncured liquid crystal phase state, Proximity exposure (proximity exposure) is preferably performed from the standpoint of preventing dust adhesion, and the occurrence of such a taper is a major problem.
(A) Since photons possessed by short wavelength active radiation have high energy, the probability of radical generation is high, and as a result, the generation amount increases, and the liquid crystal molecules are polymerized by oozing out from the exposed region of the coating film 4. from, as shown in FIG. 5 (b), the end face boundary region having a width W ₂ and disorder of the liquid crystal phase region 15a of curing is formed.
(C) The photopolymerization initiator generally has a maximum absorption wavelength in a wavelength region of 300 nm or less, and when exposed to actinic radiation having such a maximum absorption wavelength, the same as in (a) above. Polymerization of the liquid crystal molecules starts abruptly, and the end surface of the liquid crystal phase region 15a is disturbed to form a wide boundary region, as shown in FIG. Therefore, it is preferable to avoid the vicinity of the maximum absorption wavelength, and specifically include only actinic radiation having a wavelength at which the absorbance is 50% or less of the absorbance with respect to light having the maximum absorption wavelength.

  Therefore, in order to satisfy the above conditions (a) to (c), it is preferable to irradiate the coating film 4 with active radiation having a wavelength longer than the maximum absorption wavelength of the photopolymerization initiator in the light irradiation step (iii).

In general, liquid crystal molecules are polymerized and cured by ultraviolet exposure using a high pressure mercury lamp or an ultrahigh pressure mercury lamp as an irradiation device. Mainly emits light. Among these, ultraviolet rays having a wavelength of 365 nm are called i-rays, and have high irradiance irradiated from the irradiation device, and are mainly used for photopolymerization of liquid crystal molecules. On the other hand, 254 nm, 313 nm, and especially 313 nm ultraviolet light has greater light scattering than i-line, and photons have more energy than i-line. Therefore, for the reasons (a) and (b) above. It is preferable to cut. In addition, although the maximum absorption wavelength of the photopolymerization initiator differs depending on the type of the agent, it is generally closer to 313 nm than i-line (365 nm), so the light of 313 nm wavelength is cut for the reason of (c) above. It is preferable to irradiate the coating film 4 with the applied ultraviolet light.
Therefore, when using a high-pressure mercury lamp or an ultrahigh-pressure mercury lamp as an irradiation device, the light applied to the coating film 4 in the light irradiation step (iii) is limited to a wavelength exceeding 313 nm, preferably 320 nm or more, more preferably 325 nm or more. It can be said that it is preferable.
In particular, in the case of using a photopolymerization initiator having a maximum absorption wavelength of 280 nm or more and less than 320 nm, it is particularly preferable to irradiate only light having a wavelength of 320 nm or more, preferably 325 nm or more.

  As a method of limiting the wavelength of actinic radiation to, for example, 320 nm or more as described above, (a) a method of cutting light having a short wavelength of 320 nm or less by passing actinic radiation including a short wavelength through a short wavelength cut filter; In the first place, a method using an exposure machine that does not emit active radiation having a wavelength of 320 nm or less can be exemplified.

For the above method (a), a transmissive or reflective light cut filter can be used. Among these, for example, a short wavelength cut filter that cuts light of 325 nm or less or 350 nm or less is commercially available.
For example, when producing a short wavelength cut filter that cuts light of 313 nm or less or 320 nm or less, in an optical cut filter that cuts a specific wavelength by thin film interference by laminating thin films that transmit or reflect active radiation in multiple layers, A desired short wavelength cut filter can be obtained by adjusting the thickness of the thin film.
The above method (ii) can be realized by diverting an ultraviolet fluorescent lamp or a high-pressure mercury lamp for copying to an exposure machine for photopolymerization of liquid crystal molecules. These exposure machines are commercially available.

(Iv) Step of forming optically isotropic region Next, a step in which a portion that has not been irradiated with actinic radiation, that is, an unexposed region 6 in which liquid crystal molecules are not cured, is made an optically isotropic region 15b is performed. This step is different depending on whether the first or second case, that is, the optically isotropic region 15b is formed of a solid phase such as the isotropic phase region 15c or the gas phase region 15d.

(Iv-1) Isotropic phase transition step In the first case (a) in which the optically isotropic material is fixed to obtain the optically isotropic region 15b, the isotropic phase region 15c is patterned using liquid crystal molecules. In the case (a-1) to be formed, unpolymerized liquid crystal molecules contained in the unexposed region 6 are heated by heating the entire coating film 4 after irradiation with active radiation, as shown in FIG. Transition to the phase. That is, by heating the coating film 4 including the unexposed region 6 to an isotropic phase transition temperature or higher, the liquid crystal phase region 15a that has already been cured does not undergo phase transition, and only the unexposed region 6 transitions to the isotropic phase. . Note that the phase transition of the unexposed region 6 from the liquid crystal phase to the isotropic phase can be confirmed by a measuring device such as DSC or observation with a polarizing microscope.

(Iv-2) Removal step In the case of the second case (b) in which the material is not fixed and the optically isotropic region 15b is obtained by the gas phase region 15d such as air, as shown in FIG. The unexposed area 6 is removed by etching using a solvent. As the solvent, a solution capable of dissolving the polymerizable liquid crystal, particularly an organic solvent can be used.
Further, in the case (a-2) in which the optically isotropic region 15b is fixedly formed of an optically isotropic non-liquid crystalline material, the unexposed region 6 after etching is removed by using an optical material such as acrylic or urethane. What is necessary is just to fill it with an isotropic and light-transmitting resin material.

(V) Firing step In the case (a-1), as shown in FIG. 3 (5), the unexposed region 6 that has been transformed into the isotropic phase is further heated and baked to a higher temperature, so that the liquid crystal contained in the region. The isotropic phase state is fixed by polymerizing and curing the molecules. At this time, also in the liquid crystal phase region 15a fixed by photopolymerization, the three-dimensional cross-linking polymerization reaction between the liquid crystal molecules further proceeds, and the strong phase difference control layer 15 is obtained.
Therefore, it is preferable to add a thermal polymerization initiator as listed below to the coating solution.
In the present invention, the isotropic phase transition step (iv-1) and the firing step (v) may be performed simultaneously, that is, in one step.
As described above, the phase difference control layer 15 in which the liquid crystal phase region 15a and the isotropic phase region 15c are fixed by patterning is formed on the substrate 2, and thus the optical element 1 is manufactured.

Similarly, in the cases (b) and (a-2), a firing step is preferably performed to further promote the three-dimensional crosslinking polymerization of the liquid crystal phase region 15a as necessary.
Thus, the optical element 1 in which the retardation control layer 15 in which the liquid crystal phase region 15a is patterned and fixed is formed on the substrate 2 is manufactured.

  In this way, by performing the light irradiation process while limiting the wavelength of the active radiation to a predetermined or longer wavelength, the polymerizable liquid crystal molecules applied on the substrate 2 are patterned and cured at a high resolution, and the liquid crystal phase is cured. The region 15a can be fixed.

[Materials used for optical elements]
Next, each material used in the manufacturing method of the present invention will be described.

<Base material>
In the present invention, it is necessary to use a substrate having alignment ability so that a liquid crystal phase appears in the polymerizable liquid crystal molecules coated on the substrate. Examples of such a substrate having orientation ability include a case where the substrate itself has orientation ability, and a case in which an orientation film is formed on a transparent substrate and functions as a substrate having orientation ability. Can do.

  An example where the substrate itself has orientation ability is a case where the substrate is a stretched film. By using a stretched film, it is possible to align the polymerizable liquid crystal along the stretching direction. Therefore, since the preparation of the base material can be performed simply by preparing a stretched film, it has an advantage that it is extremely simple in terms of the process. As such a stretched film, a commercially available stretched film can be used, and stretched films of various materials can be formed as necessary.

  Specifically, polycarbonate polymers, polyester polymers such as polyarylate and polyethylene terephthalate, polyimide polymers, polysulfone polymers, polyethersulfone polymers, polystyrene polymers, polyolefins such as polyethylene and polypropylene Film made of thermoplastic polymer such as polymer based polymer, polyvinyl alcohol polymer, cellulose acetate polymer, polyvinyl chloride polymer, polymethyl methacrylate polymer, or film made of liquid crystal polymer. Among them, a polyethylene terephthalate (PET) film is preferable because it has a wide range of stretch ratio and is highly available.

  In addition, a base material having an alignment ability by forming an alignment film on a transparent substrate has an advantage that a relatively wide range of alignment directions can be selected by selecting an alignment treatment. By selecting the alignment treatment method of the alignment film applied on the transparent substrate, various alignment directions can be realized, and more effective alignment can be performed. As such an alignment film, an alignment film usually used in a liquid crystal display device or the like can be suitably used. In general, an alignment film is laminated on a base film, or a base film or The alignment film can be imparted with an alignment ability by rubbing or polarizing the alignment film laminated thereon. As the alignment film, polyimide, polyamide, polyvinyl alcohol or the like is usually used. In the rubbing treatment, a rubbing cloth selected from materials such as rayon, cotton, polyamide, polymethylmethacrylate, etc. is wound around a metal roll and rotated while in contact with the film, or the base is fixed with the roll fixed. A method of rubbing the film surface by rubbing by conveying the film is usually used. Moreover, the base material which has orientation ability can also be obtained by irradiating polarized light using a photo-alignment film.

  The transparent substrate is not particularly limited as long as it is formed of a transparent material. For example, a transparent rigid body having no flexibility such as quartz glass, Pyrex (registered trademark) glass, synthetic quartz plate, etc. A transparent flexible material having flexibility such as a material, a transparent resin film, an optical resin plate, or the like can be used.

  A commercially available alignment film may be used. For example, an alignment film such as Sun Ever (manufactured by Nissan Chemical Co., Ltd.), QL and LX series (manufactured by Hitachi Chemical DuPont Microsystems Co., Ltd.), AL series (manufactured by JSR Co., Ltd.), Rixon aligner (manufactured by Chisso Corporation), etc. And may be subjected to orientation treatment in the same manner as described above.

  Among the above, by providing the retardation control layer 15 obtained by the manufacturing method of the present invention on the in-cell side of the liquid crystal cell 23 in the transflective liquid crystal display device 30 as shown in FIGS. The phase difference control layer 15 can be mechanically protected by the pair of glass substrates 11 and 18, and moisture-proof deformation can be prevented. 3 and 4 is used as the glass substrates 11 and 18 of the liquid crystal display device 30 as they are, the phase difference control layer 15 has high adhesion to the glass substrates 11 and 18. Further, since no other base sheet or adhesive layer is required, the entire liquid crystal display device 30 can be thinned, and light scattering in the adhesive layer does not occur.

<Liquid crystal molecules>
The polymerizable liquid crystal molecule used in the present invention is not particularly limited as long as it is a liquid crystal material capable of forming a liquid crystal phase having nematic regularity and smectic regularity, but a nematic liquid crystal material is preferably used. Can be used. Among the nematic liquid crystal materials, nematic liquid crystals having two or more polymerizable groups in the liquid crystal molecules can be preferably used. Specifically, a polymerizable liquid crystal as disclosed in JP-T-11-513019 can be used.

  As the polymerizable liquid crystal molecule, a polymerizable monomer molecule, a polymerizable oligomer molecule, a polymerizable polymer molecule or the like may be used alone, or a mixture of two or more of these may be used.

The liquid crystal molecule preferably has an unsaturated double bond as a polymerizable functional group in its molecular structure, and has an unsaturated double bond at both ends of the molecular structure (has two or more unsaturated double bonds). Are more preferred.
Examples of the polymerizable liquid crystal molecules used for obtaining the retardation control layer 15 include nematic liquid crystal molecules having crosslinkability (crosslinkable nematic liquid crystal molecules). Examples of the crosslinkable nematic liquid crystal molecules include monomers, oligomers, and polymers having at least one polymerizable group such as a (meth) acryloyl group, an epoxy group, an octacene group, and an isocyanate group in one molecule. In addition, as such a crosslinkable liquid crystal molecule, more specifically, one or more of the compounds represented by the following chemical formulas 1 to 12 can be mixed and used.

(Wherein R ¹ and R ² each represent hydrogen or a methyl group, X represents hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group; And b each independently represents an integer of 2 to 12.)

In the compound of the above general formula (1) represented by the above chemical formula 1, it is preferable that R ¹ and R ² are both hydrogen because of the wide temperature range showing the liquid crystal phase. X is preferably a chlorine or methyl group. Furthermore, it is preferable that a and b which show the chain length of the alkylene group which is a spacer with the (meth) acryloyloxy group of both ends of a molecular chain, and an aromatic ring are respectively integers in the range of 4-10, More preferably, it is an integer in the range of 9. The compound represented by the above chemical formula 1 in which both a and b are 0 lacks stability, is susceptible to hydrolysis, and the compound itself has high crystallinity. Further, when a and b are each 13 or more, the isotropic phase transition temperature is low. For these reasons, the above-mentioned compounds in which a and b are not in the range of 2 to 12 are not preferable because the temperature range showing liquid crystallinity becomes narrow.

  In the phase difference control layer 15, the degree of polymerization of liquid crystal molecules (in the case of crosslinkable liquid crystal molecules, the degree of crosslink polymerization) is preferably about 80 or more, and more preferably about 90 or more. If the degree of polymerization of the liquid crystal molecules constituting the phase difference control layer 15 is less than 80, there is a possibility that the uniform orientation cannot be sufficiently maintained. The degree of polymerization and the degree of cross-linking polymerization indicate the proportion of the polymerizable functional group of the liquid crystal molecule consumed in the polymerization reaction of the liquid crystal molecule.

<Other ingredients>
In the present invention, the coating liquid containing a polymerizable liquid crystal preferably contains a photopolymerization initiator. As the photopolymerization initiator, a radical polymerizable initiator can be preferably used. The radical polymerizable initiator generates free radicals by energy such as ultraviolet rays. For example, benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4 -Benzoyl-4'-methyldiphenyl sulfide, benzylmethyl ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-methoxy Benzophenone, methylobenzoyl formate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morph Linophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropane-1 -One, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone , Isopropylthioxanthone, 1-chloro-4-propoxythioxanthone, and the like. In the present invention, a commercially available photopolymerization initiator can also be used. For example, Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 907 (all manufactured by Ciba Specialty Chemicals), Darocur (Merck) ), Adeka 1717 (manufactured by Asahi Denka Kogyo Co., Ltd.) and the like, and 2,2′-bis (o-chlorophenyl) -4,5,4′-tetraphenyl-1,2′biimidazole (black gold) Biimidazole compounds such as those manufactured by Kasei Co., Ltd. can be suitably used.

  In addition to the photopolymerization initiator, a sensitizer can be added within a range that does not impair the object of the present invention.

  The photopolymerization initiator is preferably added within a range that does not significantly impair the liquid crystal regularity of the polymerizable liquid crystal. The addition amount of the photopolymerization initiator is generally in the range of 0.01 to 15% by mass, preferably 0.1 to 12% by mass, more preferably 0.5 to 10% by mass with respect to the liquid crystal molecules. Can be added to the coating solution.

  In the present invention, it is preferable that the coating liquid containing a polymerizable liquid crystal further contains a thermal polymerization initiator. Although the polymerization reaction of the polymerizable liquid crystal proceeds even when heated, the polymerizable liquid crystal in an isotropic phase can be efficiently polymerized and cured by containing a thermal polymerization initiator.

  As the thermal polymerization initiator, a radical polymerizable initiator can be preferably used. For example, 2,2′-azobisisobutylnitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4 -Methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis-1-cyclohexylnitrile, dimethyl-2,2'-azobisisobutyrate, 4,4'-azobis-4-cyanovaleric acid, , 1'-azobis (1-acetoxy-1-phenylethane) and other azo compounds, benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide, 1,1-bis (tert-butylperoxy) cyclohexane and other organic compounds Mention may be made of peroxides.

  The thermal polymerization initiator is preferably added in a range that does not significantly impair the liquid crystal regularity of the polymerizable liquid crystal. The addition amount of the thermal polymerization initiator is generally 0.01 to 15% by mass, preferably 0.1 to 12% by mass, more preferably 0.5 to 10% by mass with respect to the liquid crystal molecules. It can be added to the coating solution.

  The coating liquid containing a polymerizable liquid crystal used in the present invention preferably contains a surfactant. By containing the surfactant, liquid crystal alignment at the air interface can be controlled.

  The surfactant is not particularly limited as long as it does not impair the liquid crystal expression of the polymerizable liquid crystal material. For example, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene derivative, polyoxyethylene / polyoxypropylene block polymer, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene fatty acid ester , Nonionic surfactant such as polyoxyethylene alkylamine, fatty acid salt, alkyl sulfate ester salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, alkyl phosphate, Polyoxyethylene alkyl sulfate ester salt, naphthalenesulfonic acid formalin condensate, special polycarboxylic acid type polymer surfactant, polyoxyethylene Anionic surfactants such as alkyl phosphates.

  The amount of the surfactant added is generally 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, with respect to the liquid crystal molecules.

  A polymerizable liquid crystal and each of the above components can be dissolved in a solvent to obtain a coating liquid. The solvent that can be used is not particularly limited as long as it can dissolve the polymerizable liquid crystal and each component, and an organic solvent can be suitably used. When uniformly forming a coating film on a substrate using a spin coating method, it is preferable to use one or a mixture of 3-methoxybutyl acetate, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, cyclohexanone, etc. as a solvent. Can be used.

The liquid crystal phase layer cured by light must produce a phase difference when light enters. The phase difference is determined by the retardation amount, that is, the product of the birefringence (Δn) of the liquid crystal phase layer and the film thickness. Therefore, the liquid crystal phase layer needs to be formed to have refractive index anisotropy. This refractive index anisotropy varies depending on the liquid crystal material used and the alignment ability of the substrate surface, but in general, on the plane parallel to the alignment direction, the X axis perpendicular to the alignment direction is parallel to the alignment direction. a case of assuming the Y-axis, the difference between the refractive index n _Y in refractive index n _X and Y-axis direction of the X-axis direction [Delta] n, i.e.,
(Equation 1)
Δn = | n _X −n _Y |
However, about 0.03-0.20 is preferable and about 0.05-0.15 is more preferable. When Δn is 0.03 or less, it is necessary to increase the film thickness in order to obtain a desired retardation amount, and the orientation of the liquid crystal phase layer is deteriorated. On the other hand, if Δn exceeds 0.20, the liquid crystal phase layer becomes too thin and it becomes difficult to control the film thickness. The birefringence can be measured by measuring the retardation value and the film thickness of the optical element.

  The retardation value can be measured using a commercially available optical material inspection device such as RETS-1250VA (manufactured by Otsuka Electronics Co., Ltd.). The measurement wavelength is preferably in the visible region (400 to 780 nm), and in particular, it is more preferable to measure in the vicinity of 550 nm where the relative luminous sensitivity is the highest.

  The film thickness of the optical element can be measured using a stylus profilometer or the like, and a commercially available measuring instrument such as DEKTAK (manufactured by Sloan) can be suitably used.

[About transflective liquid crystal display devices]
An example in which the optical element 1 obtained by the manufacturing method according to the present invention is incorporated in a transflective liquid crystal display device 30 and the phase difference control layer 15 is arranged on the in-cell side of the liquid crystal cell 23 is schematically shown in FIGS. Shown in

FIG. 6 is an explanatory diagram of the liquid crystal cell 23 schematically showing the transmitted light with respect to the transmissive display region 16 and the incident light and reflected light with respect to the reflective display region 17. In the figure, a gas phase region 15d is provided as the optically isotropic region 15b (second case (b): see FIG. 4).
1 and 2, the red pattern 12R, the green pattern 12G, and the blue pattern 12B that form the colored layer 12, the liquid crystal phase region 15a that forms the phase difference control layer 15, the optically isotropic region 15b, and the semi-transmissive and semi-reflective member. For convenience of explanation, the reflecting portion 24a and the opening portion 24b constituting the layer 24 are shown in stripes so as to be arranged side by side in the horizontal direction on the paper surface. Of these, the colored layer 12 is shown in FIG. As shown in FIG. 6, the stripe pattern of the phase difference control layer 15 and the semi-transmissive / semi-reflective layer 24 is actually arranged orthogonally. As a result, as shown in FIG. 6, in the width direction of the liquid crystal cell 23 (horizontal direction in the figure), strip-like color patterns are arranged in stripes in the same direction in the same direction as the desired number of pixels, and the depth direction The strip-like liquid crystal phase region 15a, the optically isotropic region 15b, the reflection portion 24a, and the opening portion 24b are repeatedly formed in stripes by the number of pairs corresponding to the desired number of pixels in the same direction. A transflective liquid crystal display device can be configured.

On the glass substrate 11, an outer edge of an effective display area and a large number of finely patterned pixels are partitioned and formed by a light-shielding black matrix (BM) 29. BM29 is a coating type resin composition containing a black colorant, vapor deposition of a multilayer chromium black matrix having a laminated structure such as CrOx / Cr or CrOx / CrNy / Cr (x and y are arbitrary numbers) After the light-shielding material is coated on the entire surface of the in-cell side of the glass substrate 11 by sputtering or the like, it can be formed into a desired shape by a photolithography method.
In the liquid crystal display device 30 of the present embodiment shown in FIGS. 1 and 2, the BM 29 covers the boundary region between the liquid crystal phase region 15a and the optically isotropic region 15b constituting the phase difference control layer 15. That is, it is formed at the boundary between the transmissive display area 16 and the reflective display area 17.
The BM 29 is generally formed with a line width of about 10 μm. Therefore, when the line width of the boundary region formed between the liquid crystal phase region 15a and the optically isotropic region 15b is 10 μm or less, the region can be covered with the BM 29, and the color shift generated in the boundary region Or light leakage will not be visually recognized by the observer. Further, by setting the line width of the boundary region to 5 μm or less, even when an error in patterning position accuracy occurs between the BM 29 and the phase difference control layer 15, the boundary region can be suitably covered with the BM 29. . Further, by setting the line width of the boundary region to 3 μm or less, there is an advantage that even when the optical element 1 does not include the BM 29 as described above, it is difficult to visually recognize color shift and light leakage.

In the liquid crystal display device 30 shown in FIG. 1, the phase difference control layer 15 is provided on the observer-side glass substrate 11. In other words, the optical element 1 has the BM 29, the colored layer 12, and the phase difference control on the in-cell side of the glass substrate 11. The layer 15 and the transparent electrode layer 14a constitute a color filter formed by coating in order.
In the liquid crystal display device 30 shown in FIG. 2, the phase difference control layer 15 is provided on the glass substrate 18 on the back side via the semi-transmissive / semi-reflective layer 24.
In any case, the optical element 1 is arranged so that the liquid crystal phase region 15a constituting the optical element 1 corresponds to the reflective display region 17, and the optical isotropic region 15b corresponds to the transmissive display region 16. The
Each configuration shown in the figure is the same as that of the conventional liquid crystal display device 30 as described above, and thus the description common to the above is omitted.

  The glass substrate 18 is formed with a pixel switching element such as a TFT, a data line, a scanning line, and the like on the in-cell side to constitute a driving liquid crystal side substrate.

  The driving liquid crystal molecules 28 such as TN liquid crystal sealed in the liquid crystal cell 23 rise in the electric field direction when a voltage is applied, and the phase shift in the liquid crystal cell 23 is caused in both the reflective display area 17 and the transmissive display area 16. It becomes zero. On the other hand, when no voltage is applied, the driving liquid crystal molecules 28 are in a lying state, and the phase shift in the liquid crystal cell 23 is ¼ wavelength in the reflective display region 17 and ½ wavelength in the transmissive display region 16. The refractive index anisotropy Δn of the driving liquid crystal molecules 28 and the layer thickness of the driving liquid crystal layer 13 are designed.

The transmission axis of the linearly polarizing plate (first polarizing plate) 10 provided on the front side of the observer and the alignment axis of the alignment film provided on the in-cell side (lower side in the drawing) of the transparent electrode layer 14a are perpendicular or parallel. In addition, when no voltage is applied, the driving liquid crystal molecules 28 are twisted 90 degrees or 270 degrees between the glass substrate 11 and the glass substrate 18.
Further, the transmission axis of the linearly polarizing plate (second polarizing plate) 19 provided on the back side and the transmission axis of the first polarizing plate 10 are orthogonal, that is, the first and second polarizing plates 10 and 19 are in a crossed Nicols state. Is configured.

  The backlight 20 includes a light source 20a, a light guide plate 20b, and a reflection plate 21. Reflection for emitting light transmitted through the light guide plate 20b toward the liquid crystal cell 23 side on the lower surface side of the light guide plate 20b. A plate 21 is provided.

  Next, the display principle of the transflective liquid crystal display device 30 will be described.

(In the case of Fig. 1)
In the voltage application state, first, visible light (external light) incident on the reflective display region 17 from the observer side passes through the first polarizing plate 10 and becomes linearly polarized light. After being split into visible light having a wavelength), a phase difference of ¼ wavelength is given when passing through the liquid crystal phase region 15 a of the optical element 1, and becomes circularly polarized light and enters the drive liquid crystal layer 13. Since no phase difference occurs in the driving liquid crystal layer 13 when a voltage is applied, the circularly polarized light passes through the driving liquid crystal layer 13 as it is.
When the circularly polarized light is reflected by the surface of the reflecting portion 24a, the polarization direction is reversed and is transmitted through the driving liquid crystal layer 13 again toward the display side. When the phase difference of ¼ wavelength is given again in the liquid crystal phase region 15a and converted into linearly polarized light, the linearly polarized light has a polarization axis perpendicular to the first polarizing plate 10, and thus the first polarized light It is absorbed by the plate 10 and is not emitted to the viewer side, and dark display is obtained.

  On the other hand, the light emitted from the backlight 20 to the transmissive display region 16 is transmitted through the second polarizing plate 19 to become linearly polarized light, and in this state, is transmitted through the liquid crystal cell 23 through the opening 24b. Since this linearly polarized light is not given a phase difference in the driving liquid crystal layer 13 and the optically isotropic region 15b when a voltage is applied, and is absorbed by the first polarizing plate 10 whose transmission axes are orthogonal to each other, a dark display is obtained. .

  In the non-voltage application state, when visible light is transmitted through the liquid crystal cell 23, the reflection display region 17 has a phase shift of ¼ wavelength due to the optical rotation of the TN liquid crystal and ¼ wavelength due to the liquid crystal phase region 15a. On the other hand, in the transmissive display region 16, a phase shift of ½ wavelength is imparted due to the optical rotation of the TN liquid crystal. Therefore, in the case of external light (reflection display) and in the case of backlight light (transmission display), the linearly polarized light transmitted through the first polarizing plate 10 has a polarization axis parallel to the polarizing plate. The emitted light is not absorbed by 10 and a bright display is obtained. That is, the liquid crystal display device 30 illustrated in the drawing is a normally white type.

  In addition, a part of the backlight light that has been linearly polarized by passing through the second polarizing plate 19 is reflected by the back surface of the reflecting portion 24a, but passes through the second polarizing plate 19 as it is toward the backlight side. Since the light is again irradiated toward the liquid crystal cell 23 by the reflecting plate 21, light can be reused and a display device with high luminance can be realized.

(In the case of Fig. 2)
In the voltage application state, first, visible light (external light) incident on the reflective display region 17 from the observer side passes through the first polarizing plate 10 and becomes linearly polarized light. After being split into visible light having a wavelength, it passes through the driving liquid crystal layer 13.
The linearly polarized light is converted into circularly polarized light with a quarter-wave phase difference when passing through the liquid crystal phase region 15 a of the optical element 1. Next, when this circularly polarized light is reflected by the surface of the reflecting portion 24a, the polarization direction is reversed. When the circularly polarized light whose polarization direction is reversed passes through the liquid crystal phase region 15a again, it is converted into linearly polarized light and passes through the liquid crystal cell 23 in this state. Since this linearly polarized light has a polarization axis perpendicular to the first polarizing plate 10, it is absorbed by the first polarizing plate 10 and is not emitted to the viewer side, resulting in dark display.

  On the other hand, the light emitted from the backlight 20 to the transmissive display region 16 passes through the second polarizing plate 19 to become linearly polarized light, and passes through the liquid crystal cell 23 in this state. Since this linearly polarized light is absorbed by the first polarizing plate 10 in the same manner as described above, it becomes a dark display.

  In the non-voltage applied state, when light is transmitted through the liquid crystal cell 23, in the reflective display region 17, a phase shift of a quarter wavelength is caused by the optical rotation of the TN liquid crystal, and a quarter wavelength is caused by the liquid crystal phase region 15a. In the transmissive display area 16, a phase shift of ½ wavelength is given due to the optical rotation of the TN liquid crystal. Therefore, in the case of external light (reflection display) and in the case of backlight light (transmission display), the linearly polarized light transmitted through the first polarizing plate 10 has a polarization axis parallel to the polarizing plate. The emitted light is not absorbed by 10 and a bright display is obtained.

  In this way, by using the optical element 1 according to the present invention in the transflective liquid crystal display device 30, the patterning of the liquid crystal phase region 15a and the optically isotropic region 15b is realized with high resolution. It is possible to prevent a halfway phase difference from being given to the transmitted light in the boundary region. As a result, it is possible to suppress a decrease in contrast ratio and a color shift due to insufficient light quantity or light leakage at the boundary between the transmissive display area 16 and the reflective display area 17. Thus, the liquid crystal display device 30 with high brightness and high contrast is manufactured. it can.

7 and 8 are schematic cross-sectional views showing modifications of the optical element 1 and the liquid crystal display device 30 of the present invention. In the optical element 1 shown in FIG. 7, a gap control layer 25 is provided on the phase difference control layer 15 coated on the observer-side glass substrate 11 so as to protrude toward the in-cell side. The gap control layer 25 is provided at a position corresponding to the reflective display region 17, and the thickness of the drive liquid crystal layer 13 in the region is designed to be half the thickness of the transmissive display region 16.
Specifically, an acrylic or urethane resin, which is a light transmissive photocurable or thermosetting resin composition, or a material mixed with an acrylic or urethane monomer is used on the retardation control layer 15. It is possible to fabricate the film by applying it onto the reflective display area 17 by photolithography and then removing it by etching in the transmissive display area 16.
Further, a transparent electrode layer 14a is formed on the upper surface of the gap control layer 25, and a voltage load for switching driving of the driving liquid crystal molecules 28 is given together with the transparent electrode layer 14b formed on the glass substrate 18 on the back side.

  The optical element 1 shown in FIG. 8 includes a phase difference control layer 15 in which the liquid crystal phase region 15 a also serves as the gap control layer 25. The phase difference control layer 15 is produced by the case (b), and the protruding height of the liquid crystal phase region 15 a corresponds to half the thickness of the driving liquid crystal layer 13. As a result, the amount of phase difference given to visible light passing through the transmissive display area 16 is twice the amount of phase difference with respect to visible light passing through the reflective display area 17.

  Note that the phase difference control layer 15 shown in FIG. 7 does not have to be etched away from the unexposed region 6 (see FIG. 3), and thus there is an advantage in the manufacturing cost of the same layer. Further, although the phase difference control layer 15 shown in FIG. 8 needs to etch away the unexposed region 6 (see FIG. 4), it is not necessary to separately stack the gap control layer 25, so that the plate making cost can be eliminated, Further, the thickness of the entire optical element 1 can be reduced.

Hereinafter, the present invention will be described in more detail with reference to examples.
(1) Production of optical element As a base material, what provided the orientation film on the glass substrate was used. Specifically, an orientation film (AL1254) manufactured by JSR Corporation was applied on a 100 × 100 mm glass substrate using a spin coater so that the film thickness was 0.065 μm, and 1 in a 230 ° C. oven. Baked for hours. Next, an alignment treatment was performed on the alignment film on the glass substrate using a rubbing apparatus.

Next, a coating solution having the following composition was applied on the obtained base material by a spin coater so that the film thickness after firing was about 2.2 μm.
<Coating solution composition>
Liquid crystal molecules (compound of (Chemical Formula 11)) 23.75 parts by weight Photopolymerization initiator (Irgacure 907) 1.25 parts by weight Solvent (diethylene glycol dimethyl ether) 75 parts by weight The maximum absorption wavelength of the photopolymerization initiator is 300 nm. It is.

Next, the substrate was held at 80 ° C., which is higher than the liquid crystal phase transition temperature of the liquid crystal molecule and lower than the isotropic phase transition temperature for 3 minutes, to bring the liquid crystal molecule into a liquid crystal phase state. The phase transition to the liquid crystal phase was confirmed by the coating film becoming transparent from cloudiness. Next, the coating film obtained above is irradiated with ultraviolet rays by an ultraviolet irradiation device through a photomask in which a transmission part and a light-shielding part are repeatedly formed in a stripe shape with a line width of 70 μm, respectively, and are present in the transmission part. The polymerizable liquid crystal molecules to be cured were three-dimensionally crosslinked and cured. As the ultraviolet irradiation device, an automatic exposure machine (manufactured by Dainippon Kaken Co., Ltd.) using an ultrahigh pressure mercury lamp as a light source was used. At this time, light having a wavelength of 400 nm, 350 nm, and 300 nm or less was cut and irradiated using a short-wavelength light cut filter (Reference Example 1, Example 1, and Comparative Example 1 respectively), and ultraviolet light was used without using the light cut filter. What was irradiated (Comparative Example 2) was produced.
The amount of ultraviolet irradiation was 200 mJ / cm ² . However, the exposure amount is measured from the illuminance of 365 nm (i-line). Moreover, in the case of the reference example 1 which cuts ultraviolet rays with a wavelength of 365 nm, it means the illuminance of irradiated light before passing through the short wavelength cut filter. In this way, a patterned liquid crystal phase layer was formed on the substrate.

  Subsequently, an optically isotropic region was produced at a position corresponding to the light shielding portion of the photomask. Specifically, according to the first case (a-1), an isotropic phase region is fixedly formed by unexposed liquid crystal molecules subjected to an isotropic phase transition (Reference Example 1a, Example 1a, Comparative Example). 1a, Comparative Example 2a), and a gas phase region formed by etching away unexposed liquid crystal molecules according to the second case (b) (Reference Example 1b, Example 1b, Comparative Example 1b, Comparative Example) 2b) were prepared respectively.

(First case (a-1))
The substrate and the coating film were held in an oven at 230 ° C. for 30 minutes and baked to polymerize and cure uncured liquid crystal molecules in an isotropic phase state. Thus, an optical element in which the liquid crystal phase region and the isotropic phase region were alternately patterned in a stripe shape was obtained (see FIG. 3).

(Second case (b))
By immersing the base material and the coating film in an organic solvent (methyl ethyl ketone), the liquid crystal molecules in an uncured state were removed by etching, and further kept in an oven at 230 ° C. for 30 minutes and baked. Thus, an optical element in which only the liquid crystal phase region was patterned in a stripe shape was obtained (see FIG. 4).

(2) Evaluation For the obtained optical element, the retardation of the liquid crystal phase region (retardation) was measured at a measurement wavelength of 550 nm using an optical material inspection device (RETS-1250VA: manufactured by Otsuka Electronics Co., Ltd.). .

In addition, with a pair of linearly polarizing plates made of crossed Nicols, the optical elements according to Reference Example 1, Example 1 and Comparative Examples 1 and 2 were sandwiched, respectively, with a polarizing microscope (Olympus Co., Ltd .: BX50). Observed. The polarizing microscope includes a color temperature conversion filter and a neutral density filter.
The observation is as follows: (i) First, all the above filters are opened to maximize the amount of light, the optical element is rotated around its normal line, and the angular position where the light transmitted from the liquid crystal phase region is minimized is the extinction position, That is, a photomicrograph was taken at the dark display position. Next, (ii) the angle position where the optical element was rotated by 45 degrees around the normal line from the extinction position was defined as the bright display position, and the photomicrograph was taken after the filter was closed to reduce the amount of light.

The photographed micrograph was converted into a gray scale by image processing, and the quality of the resolution of the liquid crystal phase region was judged by visual observation. In addition, the microphotograph is converted to black and white with five gradations by image processing, and the width of the boundary region formed between the liquid crystal phase region and the optically isotropic region is obtained by proportional calculation compared with the mask line width (70 μm). It was. As shown in FIGS. 13 and 18, the fifth gradation (black) and the second gradation are dominant in the black and white five gradation image, and therefore the fifth gradation area is optically defined. The isotropic region and the second gradation region were defined as the phase difference phase region, and the first, third, and fourth gradation regions adjacent to each other were defined as the boundary region.
In the present invention, the total width of the first, third, and fourth gradation regions determined by the above method is the width of the boundary region that substantially causes a transmitted light to have a phase difference that is less than a predetermined amount. .

(3) Results The evaluation results are summarized in Table 1 below.

(Table 1)

Regarding Examples 1a and 1b, it was confirmed that light was transmitted from the liquid crystal phase region and light was not transmitted from the optically isotropic region. Moreover, the retardation measured with the optical material inspection apparatus was about 300 nm.
The grayscale images at the dark display position and the bright display position of Example 1a are shown in FIGS. Similarly, gray scale images at the dark display position and the bright display position of Example 1b are shown in FIGS. FIG. 13 shows a black and white five-tone image at the bright display position of Example 1b. From the figure, in the case of Example 1b, the width of the boundary region observed with the polarizing microscope was 1 μm or less.

On the other hand, in Reference Examples 1a and 1b, the liquid crystal molecules are not sufficiently photopolymerized due to the i-line (365 nm wavelength light) being cut from the irradiation light, and the liquid crystal phase region is eroded or baked by the subsequent etching process. Due to the phase transition of the liquid crystal molecules due to the process, sufficient retardation could not be obtained.
In Comparative Examples 1a, 1b and 2a, 2b, although sufficient retardation of about 300 nm was obtained, the boundary region was formed wide and the resolution was poor.
Gray scale images at the dark display position and the bright display position of Comparative Example 2a are shown in FIGS. Similarly, gray scale images at the dark display position and the bright display position of Comparative Example 2b are shown in FIGS. FIG. 18 shows a black and white five-tone image at the bright display position of Comparative Example 2b. From the figure, in the case of Comparative Example 2b, a boundary region having a width of about 26 μm was observed by observation with a polarizing microscope.

  From the above, the embodiment of the present invention in which ultraviolet rays having a wavelength shorter than that of the i-line are cut and irradiated can obtain a retardation control layer with sufficient retardation and improved patterning resolution in the liquid crystal phase region. confirmed.

It is a cross-sectional schematic diagram which shows an example of the transflective liquid crystal display device 30 provided with the optical element 1 by this invention. It is a cross-sectional schematic diagram which shows another example of the transflective liquid crystal display device 30 provided with the optical element 1 by this invention. It is a schematic diagram which shows the manufacturing method of the optical element 1 concerning a 1st case (a). It is a schematic diagram which shows the manufacturing method of the optical element 1 concerning a 2nd case (b). It is a schematic diagram of the boundary area | region formed in the boundary of the liquid crystal phase area | region 15a and the optically isotropic area | region 15b. FIG. 4 is an explanatory diagram of a liquid crystal cell that schematically shows transmitted light with respect to a transmissive display region and incident light and reflected light with respect to a reflective display region. 6 is a schematic cross-sectional view showing a modification of the optical element 1 and the liquid crystal display device 30. FIG. 6 is a schematic cross-sectional view showing a modification of the optical element 1 and the liquid crystal display device 30. FIG. It is a gray scale image in the dark display position of Example 1a. It is a gray scale image in the bright display position of Example 1a. It is a gray scale image in the dark display position of Example 1b. It is a gray scale image in the bright display position of Example 1b. It is a monochrome 5 gradation image in the bright display position of Example 1b. It is a gray scale image in the dark display position of the comparative example 2a. It is a gray scale image in the bright display position of the comparative example 2a. It is a gray scale image in the dark display position of the comparative example 2b. It is a gray scale image in the bright display position of the comparative example 2b. It is a monochrome 5 gradation image in the bright display position of the comparative example 2b.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical element 2 Base material 3 Orientation film 4 Coating film 5 Photomask 6 Unexposed area | region 11,18 Glass substrate 15 Phase difference control layer 15a Liquid crystal phase area | region 15b Optical isotropic area | region 15c Isotropic phase area | region 15d Gas phase area | region 16 Transmission | permeation Display area 17 Reflective display area 23 Liquid crystal cell 24 Transflective semi-reflective layer 24a Reflector 24b Opening 30 Transflective semi-reflective liquid crystal display device

Claims (4)

A method of manufacturing an optical element in which a liquid crystal phase region that causes a phase difference in transmitted light is patterned on a light-transmitting substrate,
(I) an application step of applying a coating liquid containing polymerizable liquid crystal molecules and a photopolymerization initiator on the substrate to form a coating film;
(Ii) an alignment step of aligning the liquid crystal molecules in a liquid crystal phase state;
(Iii) A light irradiation step of patterning the liquid crystal phase region by polymerizing and curing the irradiated liquid crystal molecules by irradiating the liquid crystal molecules in the liquid crystal phase state with actinic radiation through a photomask.
Only it contains, and,
The wavelength of light substantially contained in the active radiation that is irradiated with the pattern in the light irradiation step is longer than the maximum absorption wavelength of the photopolymerization initiator,
The absorbance of the photopolymerization initiator with respect to the light having the shortest wavelength substantially contained in the active radiation irradiated with the pattern is 50% or less of the absorbance with respect to the light having the maximum absorption wavelength. Device manufacturing method. The method according to claim 1, wherein an isotropic phase region that does not cause a phase difference in transmitted light is patterned on the base material together with the liquid crystal phase region.
After the light irradiation step (iii),
(Iv-1) an isotropic phase transition step of heating the coating film in which the liquid crystal phase region is patterned to bring uncured liquid crystal molecules into an isotropic phase; and
(V) a firing step of forming the isotropic phase region by thermally polymerizing the liquid crystal molecules in the isotropic phase;
A method for manufacturing an optical element , characterized in that: After the light irradiation step (iii),
(Iv-2) A removal step of removing uncured liquid crystal molecules from the coating film in which the liquid crystal phase region is patterned.
The method of manufacturing an optical element according to claim 1, wherein: The method for producing an optical element according to claim 1, wherein the coating liquid further comprises a thermal polymerization initiator .