JP6665420B2 - Optical film - Google Patents

Description

  The present invention relates to a novel configuration of an optical film having a positive C plate.

  As an optical film applied to a flat panel display or the like, there is provided an optical film which imparts a desired retardation to transmitted light by a retardation layer to secure desired optical characteristics (for example, see Patent Document 1). In this type of optical film, an alignment film is formed on the surface of a substrate made of a transparent film or the like, and the liquid crystal material is cured by an alignment regulating force of the alignment film to form a retardation layer.

  Although the liquid crystal material applied to such a retardation layer usually has a positive wavelength dispersion characteristic, recently, a liquid crystal material having an inverse wavelength dispersion characteristic has been proposed (for example, see Patent Documents 2 and 3). ). Here, the inverse wavelength dispersion characteristic is a wavelength dispersion characteristic in which the phase difference in the transmitted light is smaller on the shorter wavelength side, and more specifically, the retardation (R450) at a wavelength of 450 nm and the retardation (R550) at a wavelength of 550 nm. And R450 <R550.

  Further, in an image display panel, a method of improving various optical characteristics such as a viewing angle characteristic and a color using an A plate, a C plate and the like has been proposed. A device relating to optical compensation of an IPS liquid crystal display device using a C plate has been proposed. Here, the optical compensation is a configuration for reducing light leakage in an oblique direction from a linear polarizing plate during black display. The C plate is represented by nx = ny <nz or nx = ny> nz, where nx = ny <nz is a positive C plate and nx = ny> nz is a negative C plate.

  The positive C plate can be manufactured by applying a coating liquid of a so-called C plate liquid crystal material, followed by drying and curing. In a vertical alignment (VA) liquid crystal display device and the like, a liquid crystal material is vertically aligned by a vertical alignment film, and various devices for a vertical alignment film for a VA liquid crystal have been proposed (for example, Patent Documents 5 to 5). 10).

  Now, in the case of an optical film having a positive C-plate, an optical film that provides a 1/4 wavelength phase difference in a high wavelength region is required in accordance with the trend of high contrast, thin film, and low cost of a liquid crystal display. For example, there has been proposed a method of manufacturing an optical film using a special polycarbonate resin exhibiting reverse wavelength dispersion characteristics.

  Conventionally, as an optical film using a polycarbonate resin exhibiting such reverse wavelength dispersion characteristics, a vertical alignment film is provided on a substrate made of the polycarbonate, and a liquid crystal material is applied on the vertical alignment film to form a retardation layer. (Liquid crystal layer) and the liquid crystal was vertically aligned to form a retardation layer.

  However, in recent years, there has been a demand for an optical film having a positive C plate, which is even thinner and lower in cost.

JP-A-10-68816 US Patent No. 8119026 JP 2010-522892 A JP 2006-520008 A JP 2011-227484 A JP 2012-163945 A JP-A-2004-83810 JP 2009-258665 A JP 2006-337958 A JP 2005-308924 A

  The present invention has been proposed in view of such circumstances, and shows an optical film having a positive C plate, which shows a good orientation as in the past and can be manufactured at lower cost. The purpose is to provide.

  The present inventor has conducted intensive studies in order to solve the above-mentioned problems. As a result, a coating liquid comprising a liquid crystal composition containing a specific solvent was applied to an optical film provided with a positive C plate having a polycarbonate base material exhibiting reverse wavelength dispersion characteristics. By forming the retardation layer (liquid crystal layer), an optical film having high adhesion and excellent alignment for vertically aligning the liquid crystal compound can be obtained without providing a vertical alignment film as in the related art. That is, the present invention has been completed. That is, the present invention provides the following.

  (1) The first invention of the present invention is an optical film comprising a polycarbonate having reverse wavelength dispersibility as a base material, wherein the optical film contains a permeation layer and a polymerizable liquid crystal composition on the base material of the polycarbonate. And a liquid crystal layer formed by sequentially laminating, the permeation layer is formed by dissolving the polycarbonate constituting the base material by a solvent contained in the polymerizable liquid crystal composition. It is an optical film.

  (2) A second invention of the present invention is the optical film according to the first invention, wherein the liquid crystal layer does not contain a component dissolved by the solvent in the polycarbonate.

  (3) The third invention of the present invention is the method according to the first or the second invention, wherein the solvent has an evaporation rate ratio of butyl acetate to the evaporation rate of 1 or more and 3 or less, and a polycarbonate substrate test piece (2 × 2 cm) is an optical film containing, as a main component, a solvent in which the time required for dissolution is 20 minutes or less.

  (4) A fourth invention of the present invention is the optical film according to the third invention, wherein the solvent contains methyl isobutyl ketone (MIBK) as a main component as the solvent.

  ADVANTAGE OF THE INVENTION According to this invention, the optical film of a novel structure which makes the base material which consists of polycarbonate and a retardation layer adhere effectively, and shows favorable orientation without providing a vertical alignment film conventionally is provided. can do.

It is sectional drawing which shows an example of a structure of an optical film. It is the observation image observed by the STEM of the cross section of an optical film by 50,000-fold visual field. FIG. 5 is a graph showing the measurement results of the evaporation rate (rate ratio when butyl acetate = 1) and the dissolution time (min) of a polycarbonate substrate for several types of solvents. It is a flowchart which shows the flow of the manufacturing process of an optical film. It is sectional drawing which shows the structure of the liquid crystal display device used for examination of the optical function film. It is sectional drawing which shows an example of a structure of an optical function film. 3 is an observation image (50,000 magnification) obtained by observing a cross section of the optical film obtained in Example 1 with a STEM. 5 is an observation image (magnification: 50,000) obtained by observing a cross section of the optical film obtained in Example 2 with a STEM. 5 is an observation image (magnification: 50,000) of a cross section of the optical film obtained in Comparative Example 1 observed by STEM.

Hereinafter, specific embodiments of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail in the following order with reference to the drawings. Note that the present invention is not limited to the following embodiments, and various changes can be made without changing the gist of the present invention.
1. 1. Structure of optical film 2. Manufacturing method of optical film (C plate) Optical film with C plate

≪1. Structure of optical film≫
FIG. 1 is a cross-sectional view illustrating an example of the configuration of the optical film according to the present embodiment. In the present embodiment, for example, in an image display device, by arranging the optical film 1 together with various optical films on the viewer side of the liquid crystal display panel, various optical characteristics can be improved. Here, the improvement of the optical characteristics refers to, for example, improvement of the viewing angle characteristics, optical compensation for reducing light leakage in oblique directions, correction of tint, and the like.

  The optical film 1 is a positive C plate having optical characteristics of nx = ny <nz, and has wavelength dispersion characteristics of inverse wavelength dispersion (hereinafter, also referred to as “reverse dispersion characteristics”). More specifically, the phase difference (Re0 (λ)) at 0 degree incidence at a wavelength λ of 450 nm to 650 nm is 20 nm or less, and the phase difference (Reθ (λ)) at an oblique incidence angle θ (θ> 0) is 0 degree. It is larger than the phase difference of incidence (Re0 (λ)), and thereby functions as a positive C plate. Further, as the wavelength λ further increases, the film has optical characteristics in which the phase difference (Reθ (λ)) of the oblique incident angle θ (θ> 0) increases, thereby functioning as a film exhibiting reverse dispersion characteristics. From this, the image display device provided with this optical film can secure desired optical characteristics in a wide wavelength band.

  Specifically, the optical film 1 according to the present embodiment uses, as the base material 11, a base material made of polycarbonate exhibiting reverse wavelength dispersion characteristics. In the optical film 1, the liquid crystal layer 13 is formed by applying a coating liquid composed of a polymerizable liquid crystal composition containing a specific solvent on the base material 11. The optical film 1 has a permeation layer 12 formed between a substrate 11 and a liquid crystal layer 13 by dissolving the polycarbonate constituting the substrate 11 with a solvent contained in the polymerizable liquid crystal composition. As described above, according to the optical film 1 having the configuration (laminated body) in which the base material 11, the permeable layer 12, and the liquid crystal layer 13 are sequentially laminated, the optical film 1 can be manufactured at low cost without providing a vertical alignment film as in the related art. , Can function as a positive C plate.

  FIG. 2 is a STEM observation image (magnification: 50,000) of a cross section of the optical film 1 according to the present embodiment. As shown in this observation image, a permeation layer 12 is formed between the base material 11 and the liquid crystal layer 13. 2A and 2B are based on the difference in the solvent component in the polymerizable liquid crystal composition constituting the liquid crystal layer 13, and will be described in detail in Examples.

<1-1. Substrate>
As the substrate 11, a substrate made of polycarbonate exhibiting reverse wavelength dispersion characteristics is used. By using such a base material made of polycarbonate, the optical anisotropy is small and it can be suitably used as a C plate.

  Here, although described later in detail, in the optical film 1 according to the present embodiment, the permeable layer 12 is formed between the base material 11 and the liquid crystal layer 13. The penetrating layer 12 is located near the substrate 11 side, and the solvent contained in the liquid crystal composition constituting the liquid crystal layer 13 penetrates into the substrate 11 and the polycarbonate constituting the substrate 11 is dissolved. It is a layer formed by this. As described above, the optical film 1 has the osmotic layer 12 formed by dissolving a part of the polycarbonate which is a constituent component of the base material 11. By exhibiting the effect, the adhesion between the substrate 11 and the liquid crystal layer 13 can be improved.

<1-2. Liquid Crystal Layer>
The liquid crystal layer 13 is a layer having an optical function as a C plate, and is a liquid crystal material used for producing retardation layers of various optical films, and includes a liquid crystal compound whose wavelength dispersion property is, for example, inverse dispersion property. It is formed by applying a polymerizable liquid crystal composition to the substrate 11. In the liquid crystal layer 13, the liquid crystal compound is vertically (homeotropic) aligned.

[About polymerizable liquid crystal composition]
Specifically, the polymerizable liquid crystal composition contains a liquid crystal compound (rod compound) having liquid crystallinity and having a polymerizable functional group in the molecule.

(Liquid crystal compound)
The liquid crystal compound has a refractive index anisotropy, and has a function of imparting a desired retardation by being regularly arranged. As the liquid crystal compound, for example, a material exhibiting a liquid crystal phase such as a nematic phase and a smectic phase may be mentioned.However, the nematic phase is easily compared with other liquid crystal compounds exhibiting a liquid crystal phase. It is more preferable to use the liquid crystal compound shown. As the liquid crystal compound exhibiting a nematic phase, a material having spacers at both ends of the mesogen is preferably used. Liquid crystal compounds having spacers at both ends of the mesogen have excellent flexibility.

  Further, the liquid crystal compound is a polymerizable liquid crystal compound having a polymerizable functional group in a molecule as described above. By having a polymerizable functional group, it becomes possible to polymerize and fix the liquid crystal compound, so that the alignment stability is excellent and the change in retardation with time hardly occurs. Further, the polymerizable liquid crystal compound more preferably has a polymerizable functional group capable of three-dimensionally crosslinking in the molecule. By having a polymerizable functional group capable of three-dimensional cross-linking, sequence stability can be further enhanced. In addition, "three-dimensional crosslinking" means that liquid crystalline molecules are three-dimensionally polymerized with each other to form a network structure.

  Examples of the polymerizable functional group include those that polymerize by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat. These polymerizable functional groups include radical polymerizable functional groups. Representative examples of the radical polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include a vinyl group having or not having a substituent and an acrylate group. (General term including acryloyl group, methacryloyl group, acryloyloxy group, and methacryloyloxy group).

  Further, the liquid crystal compound particularly preferably has a polymerizable functional group at a terminal. By using such a liquid crystal compound, for example, it is possible to polymerize three-dimensionally with each other to form a network (network) structure, so that the liquid crystal compound has column stability and is excellent in expressing optical characteristics. A C plate can be formed.

  The content of the liquid crystal compound in the polymerizable liquid crystal composition is not particularly limited as long as the viscosity of the polymerizable liquid crystal composition can be adjusted to a desired value according to a coating method for coating on the substrate 11. It is preferably contained in the composition at a ratio of 5 parts by mass to 40 parts by mass, more preferably at a ratio of 10 parts by mass to 30 parts by mass. If the amount of the liquid crystal compound is less than 5 parts by mass, the incident light to the liquid crystal layer 13 may not be properly aligned because the content is too small. On the other hand, when the amount exceeds 40 parts by mass, the viscosity of the polymerizable liquid crystal composition becomes too high, so that the workability deteriorates.

  The liquid crystal compounds can be used alone or in combination of two or more.

(solvent)
The above-mentioned liquid crystal compound is usually dissolved in a solvent. The solvent needs to be capable of uniformly dispersing the above-mentioned liquid crystal compound. In the optical film 1 according to the present embodiment, the solvent contained in the polymerizable liquid crystal composition has a relatively high evaporation rate and a short time to completely dissolve the polycarbonate constituting the base material 11. A solvent having the following formula:

Specifically, as the solvent, a polycarbonate substrate having an evaporation rate ratio (when butyl acetate = 1) to the evaporation rate of butyl acetate of 1 or more and 3 or less and measured by the following test method is used. A solution containing a solvent having a dissolution time of 20 minutes or less as a main component is used. In addition, the main component means that the content in the solvent is 51% or more by mass ratio, preferably 60% or more, more preferably 70% or more.
<Method of measuring dissolution time of solvent>
The solvent is placed in a 5 g glass bottle, a 2 cm × 2 cm test piece of a polycarbonate substrate is charged, and the time until the test piece is completely melted is measured. The faster the dissolution time (the shorter the dissolution time), the higher the solubility in the substrate.

  FIG. 3 is a graph showing the measurement results of the evaporation rate (rate ratio when butyl acetate = 1) and the dissolution time (min) of the polycarbonate substrate for several types of solvents. As described above, the faster the dissolving time, the higher the solubility in the substrate. The evaporation rate is a rate ratio based on butyl acetate, and a larger value means a lower evaporation rate, that is, a longer time until drying.

  Here, the optical film 1 according to the present embodiment has the permeable layer 12 between the base material 11 and the liquid crystal layer 13, and the permeable layer 12 is formed of a polymerizable liquid crystal composition constituting the liquid crystal layer 13. It is formed by dissolving the polycarbonate constituting the base material 11 with the solvent contained in the product. That is, the osmotic layer 12 is composed of a component dissolved by the polycarbonate solvent. In the optical film 1, by providing such a permeation layer 12, the permeation layer 12 exerts an anchor effect, enhances adhesion between the base material 11 and the liquid crystal layer 13, and exhibits good alignment.

  For this reason, it is preferable that the solvent contained in the polymerizable liquid crystal composition has good solubility in polycarbonate (has a high dissolution rate), thereby forming the permeable layer 12. Become. Specifically, it is preferable to use a solvent having a dissolution time of 20 minutes or less. On the other hand, from the viewpoint of the evaporation rate of the solvent, if the evaporation rate is too slow (the evaporation rate ratio with respect to butyl acetate is too large), it takes a long time to dry when drying under predetermined drying conditions. In other words, the dissolved polycarbonate component (dissolved component) does not stay in the vicinity of the substrate 11 but drifts toward the surface (exposed surface) of the liquid crystal layer 13. Then, due to the dissolved component of the polycarbonate contained in the liquid crystal layer 13, the orientation thereof is deteriorated. For this reason, it is preferable that the evaporation rate is also appropriately high, and specifically, it is preferable that the rate of the rate with respect to butyl acetate (= 1) is 3 or less. If the evaporation rate ratio is less than 1, the evaporation rate is too fast to dissolve the polycarbonate effectively and the permeation layer 12 is not formed. Therefore, the evaporation rate ratio is preferably 1 or more.

  More specifically, it is preferable that the solvent contains methyl isobutyl ketone (MIBK) as a main component. For example, as a composition of the solvent, a solvent containing MIBK at a ratio of 100% by mass in the solvent, and a mixed solvent containing MIBK: cyclopentyl methyl ether (CPME) = 70 to 95: 5 to 30 are used. Can be.

  In the present embodiment, by selecting the solvent contained in the polymerizable liquid crystal composition constituting the liquid crystal layer 13, the osmotic layer 12 is formed between the base material 11 made of polycarbonate and the liquid crystal layer 13. And the adhesion between the base material 11 and the liquid crystal layer 13 can be enhanced. Further, by appropriately selecting the solvent, the dissolved component of the polycarbonate is prevented from drifting in the liquid crystal layer 13 and good alignment is exhibited (the liquid crystal compound is vertically aligned well). That is, in the optical film according to the present embodiment, the liquid crystal layer 13 does not include a component dissolved by the polycarbonate solvent. The presence or absence of the dissolved component of polycarbonate in the liquid crystal layer 13 can be easily measured by, for example, IR measurement.

  The content of the solvent in the polymerizable liquid crystal composition is preferably from 66 parts by mass to 900 parts by mass based on 100 parts by mass of the liquid crystal compound. If the amount of the solvent is less than 66 parts by mass, the liquid crystal compound may not be dissolved uniformly. On the other hand, if the amount exceeds 900 parts by mass, a part of the solvent may remain and the reliability may be reduced, and the coating may not be performed uniformly.

(Other additives)
Note that the polymerizable liquid crystal composition can contain other additives as necessary. Other compounds are not particularly limited as long as they do not impair the arrangement order of the liquid crystal compound described above.For example, a polymerization initiator, a polymerization inhibitor, a plasticizer, a surfactant, a silane coupling agent, and the like may be used. Can be mentioned. For example, a radical polymerization initiator can be contained as a polymerization initiator.

[Method of forming liquid crystal layer]
The liquid crystal layer 13 is formed by applying a coating liquid composed of a polymerizable liquid crystal composition constituting the liquid crystal layer 13 on the base material 11 composed of polycarbonate, and then drying it under predetermined drying conditions, and irradiating with ultraviolet rays, electron beams, or the like. And can be formed by curing.

  The method for applying the coating liquid comprising the polymerizable liquid crystal composition onto the substrate 11 is not particularly limited, and examples thereof include a die coating method, a gravure coating method, a reverse coating method, a knife coating method, and a dip coating method. Method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, dipping and pulling method, curtain coating method, casting method, bar coating method, extrusion coating method, E-type coating method, etc. Can be.

  The curing treatment for polymerizing and curing the liquid crystal compound can be performed by irradiating active radiation such as ultraviolet rays or electron beams. The actinic radiation is not particularly limited as long as the actinic radiation can polymerize the liquid crystal compound, but usually, it is preferable to use ultraviolet light from the viewpoint of easiness of the apparatus. By performing such a curing treatment, the liquid crystal compounds are polymerized with each other to form a network structure, and the liquid crystal layer 13 having column stability and exhibiting excellent optical characteristics. Can be formed.

  For example, when ultraviolet rays are used as actinic radiation, the light sources include low-pressure mercury lamps (germicidal lamps, fluorescent chemical lamps, black lights), high-pressure discharge lamps (high-pressure mercury lamps, metal halide lamps), and short arc discharge lamps (ultra-high pressure mercury lamps). Lamp, xenon lamp, mercury xenon lamp) and the like. Among them, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp and the like can be preferably used.

The wavelength of the ultraviolet light is appropriately set according to the liquid crystal material or the like. Specifically, irradiation light having a wavelength of 210 nm to 380 nm, preferably 230 nm to 380 nm, and more preferably 250 nm to 380 nm is used. Is preferred. As the irradiation amount of the ultraviolet (integrated light quantity) is not particularly limited, for ^example, 100 J / cm 2 is preferably in the range of ~1500mJ / cm ^2, within a range of 100mJ / cm ² ~800mJ / cm 2 Is more preferable.

[About the thickness of the liquid crystal layer]
The thickness of the liquid crystal layer 13 is not particularly limited, but is preferably, for example, about 500 nm to 2000 nm in order to obtain appropriate alignment performance.

<1-3. Permeation layer>
As described above, the optical film 1 according to the present embodiment has the penetrating layer 12 between the base material 11 and the liquid crystal layer 13 (see the STEM observation image in FIG. 2). The permeable layer 12 is composed of a dissolved component in which the polycarbonate of the base material 11 is dissolved by the solvent contained in the polymerizable liquid crystal composition constituting the liquid crystal layer 13.

  More specifically, by applying the polymerizable liquid crystal composition constituting the liquid crystal layer 13 onto the base material 11, the solvent contained in the composition permeates the base material 11, and the solvent causes the base material 11 to pass through. The constituting polycarbonate is dissolved, and the permeable layer 12 is formed from the dissolved component.

  As described above, in the optical film 1, the provision of the osmotic layer 12 made of a component dissolved by the solvent of the polycarbonate provides an anchor effect, thereby improving the adhesion between the base material 11 and the liquid crystal layer 13. In addition, by setting the solvent of the polymerizable liquid crystal composition constituting the liquid crystal layer 13 to an appropriate solvent as described above, good alignment can be exhibited. Thus, an optical film including a positive C plate can be manufactured at low cost without providing a vertical alignment film on a substrate as in the related art.

{2. Manufacturing method of optical film (C plate)
Next, a method for manufacturing the optical film 1 having the above-described configuration will be briefly described. FIG. 4 is a flowchart showing the flow of the manufacturing process of the optical film 1.

  As shown in FIG. 4, in the manufacturing process of the optical film 1, first, the base material 11 made of polycarbonate is provided by a roll (step SP1).

  Next, the base material 11 is pulled out from the supply reel, and is formed of a polymerizable liquid crystal composition that forms the liquid crystal layer 13 by a die or the like on the base material 11 in a coating step of a liquid crystal layer forming coating liquid (step SP2). A coating liquid (liquid crystal layer forming coating liquid) is applied.

  Next, as a drying step, the coating film for forming a liquid crystal layer applied on the base material 11 is dried under predetermined conditions. Drying conditions can be performed, for example, by setting the drying temperature to 40 ° C. to 60 ° C., setting the drying time to 1 minute to 15 minutes, and blowing air at a wind speed of 5.0 m / s to 10.0 m / s. .

  Here, in the present embodiment, as a solvent in the polymerizable liquid crystal composition, preferably, the evaporation rate ratio of butyl acetate to the evaporation rate is 1 or more and 3 or less, and a test piece (2 × 2 cm) is used as a main component. Specifically, for example, a solvent containing MIBK as a main component is used. Then, a coating liquid comprising the polymerizable liquid crystal composition is applied onto a substrate 11 comprising polycarbonate to form a liquid crystal layer 13.

  Therefore, after coating on the substrate 11, the solvent in the polymerizable liquid crystal composition dissolves the polycarbonate, and until the solvent evaporates by the drying treatment in this drying step (step SP3), the dissolved component of the polycarbonate Is formed on the base material 11. That is, the drying step (step SP3) is also a step of forming the permeable layer 12.

  Next, after the coating liquid for forming a liquid crystal layer is dried, as a liquid crystal layer forming step (step SP4), the coating film is cured by applying irradiation treatment with ultraviolet rays or the like or heating treatment. To form Through such steps, the C plate 1 can be manufactured.

{3. Optical film to which C plate is applied.
Next, an optical functional film to which the above-described optical film (C plate) is applied will be described. In this optical function film, a C plate is integrally formed with various optical function films disposed on the image display panel, and the configuration of the optical film 1 described above is applied as the C plate.

<3-1. Example of liquid crystal display device having optical film>
Here, the liquid crystal layer 13 of the optical film 1 described above is laminated on the surface of the member where the positive C plate is disposed. As such an optical functional film, various structures such as a film made of a linear polarizing plate disposed on an emission surface of a liquid crystal display panel and a film in which the linear polarizing plate and a color filter are integrated can be widely applied. In addition, in the case of a film made of a linear polarizing plate disposed on the emission surface of a liquid crystal display panel or a film in which this linear polarizing plate and a color filter are integrated, various types of optical compensation using a C plate have been proposed. The optical film 1 described above can be applied.

  FIG. 5 is a cross-sectional view illustrating a configuration of a liquid crystal display device used for studying an optical functional film. In the liquid crystal display device 2 shown in FIG. 5, the optical function film 21 is obtained by applying a C plate to an optical film in which a linear polarizing plate and a color filter disposed on the exit surface of the liquid crystal display panel are integrated and optically compensated. It is an example to be provided for.

  The liquid crystal display device 2 is an IPS liquid crystal display device (IPS-LCD), and a liquid crystal display panel 23 is disposed in front of a backlight 22.

  The liquid crystal display panel 23 is provided with a liquid crystal cell 24 made of IPS liquid crystal, and a linear polarizing plate 25 is provided on the backlight side of the liquid crystal cell 24 by, for example, a pressure-sensitive adhesive layer (not shown). The linear polarizing plate 25 is configured by sandwiching a polarizer 25B, which is a liquid crystal layer serving as a linear polarizing plate, between substrates 25A and 25C made of a transparent film.

  In the liquid crystal display panel 23, the optical function film 21 is disposed on the emission surface of the liquid crystal cell 24. The optical function film 21 includes an optical compensation layer 26 for optical compensation, a polarizer 27, and a base material (protective film) 28 as a surface material. The optical compensation layer 26 is formed of a positive (+) C plate (hereinafter, also referred to as “+ C plate 26”). As the base material 28, a transparent film such as TAC is applied, and a liquid crystal layer as a linear polarizing plate is provided like the linear polarizing plate 25. In the optical function film 21, the polarizer 27 is formed by the liquid crystal layer, and the base material 28 and the polarizer 27 constitute a linear polarizing plate on the emission surface side.

  The + C plate 26 in such a laminate is constituted by a laminate (optical film 1) in which the above-described base material 11 / (penetration layer 12) / liquid crystal layer 13 are laminated in this order.

<3-2. Optical Function Film>
Next, the optical function film 21 in the liquid crystal display device 2 described above will be described more specifically. FIG. 6 is a cross-sectional view illustrating a configuration example of the optical function film 21 described above. As shown in FIG. 6, as the optical function film 21, a C plate 26 in which the base material 11 and the liquid crystal layer 13 are sequentially laminated (the “optical film 1” in the above description. 26 (1) "), and a polarizer 27 is laminated on the C plate 26 (1) via an adhesive layer 30 made of a UV adhesive or the like. A substrate (protective film) 28 made of a TAC film or the like is bonded.

  As described above, the C plate 26 constituting the optical function film 21 includes the base material 11 and the liquid crystal layer 13 and does not include a vertical alignment film as in the related art. In the C plate 26 in the present embodiment, the substrate 11 made of polycarbonate is used, and the solvent in the polymerizable liquid crystal composition constituting the liquid crystal layer 13 penetrates between the substrate 11 and the liquid crystal layer 13. And a permeable layer 12 made of a dissolved component obtained by dissolving the polycarbonate. Thereby, even if the vertical alignment film is not provided, the base material 11 and the liquid crystal layer 13 can be effectively brought into close contact with each other, and good alignment can be exhibited, and the C plate 26 can be made thinner than before. And can be manufactured at low cost.

  In addition, in the C plate 20 (1), the permeable layer 12 is made of a dissolved component of polycarbonate as described above, and is different from a conventional vertical alignment film. ) ", And the interface between the permeation layer (12) and the liquid crystal layer 13 is also indicated by a dotted line in the sectional configuration view.

  The adhesive layer 30 is laminated on the C plate 26 (1) as described above, and the polarizer 27 is attached to the C plate 26 (1) via the adhesive layer 30. The adhesive layer 30 is mainly formed by curing a two-part adhesive composition composed of a main agent and a curing agent. Although the main agent is not particularly limited, for example, a UV adhesive layer can be formed using an ultraviolet curable resin. More specifically, examples of the ultraviolet curable resin include an acrylic resin, a silicone resin, an ester resin, a urethane resin, etc., and pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and polyfunctional. Urethane acrylate and the like are preferably used. Among them, it is particularly preferable to use dipentaerythritol hexaacrylate.

  The polarizer 27 is adhered on the above-mentioned adhesive layer 30 and is attached to the C plate 26 (1) via the adhesive layer 30. The polarizer 27 is not particularly limited and a known polarizer can be used. For example, a dichroic material such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film. And uniaxially stretched, and a polyene-based oriented film such as a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product.

  Hereinafter, the present invention will be described in more detail by showing Examples, but the present invention is not limited to the following Examples.

[Example 1]
(Preparation of optical film)
Using an organic solvent MIBK (content in the solvent: 100% by mass) as a solvent, a liquid crystal compound exhibiting a nematic phase (manufactured by DIC Corporation) and 2-hydroxy-3-phenoxypropyl acrylate, which is a UV-curable monomer ( M600A (manufactured by Kyoeisha Chemical Co., Ltd.) so as to have a solid content ratio of 24% to prepare a polymerizable liquid crystal composition.

  A coating liquid composed of the adjusted polymerizable liquid crystal composition was applied by a die coating method on a protective back surface of a polycarbonate substrate (RM147, manufactured by Teijin Limited) having reverse wavelength dispersion characteristics.

Thereafter, a drying treatment is performed by blowing air under the conditions of a drying atmosphere temperature: 40 ° C., a time: 1 minute, and a wind speed: 5.0 m / s, and the coating film is irradiated with ultraviolet rays having an irradiation amount of 400 mJ / cm ^2. Cured. Thus, an optical film in which a liquid crystal layer was laminated on a substrate made of polycarbonate was obtained.

(STEM observation)
FIG. 7 is an observation image (magnification: 50,000) obtained by observing a cross section of the obtained optical film by STEM. Note that the observation image in FIG. 7 is the same as the observation image in FIG. As can be seen from this observation image, it can be seen that a penetrating layer is formed between the substrate made of polycarbonate and the liquid crystal layer.

(Adhesion evaluation)
The optical film was evaluated for adhesion between the substrate and the liquid crystal layer. The evaluation of the adhesion was performed by performing a cross cut (100 squares) according to JIS K5400-8.5 method using a mending tape (manufactured by Sumitomo 3M Limited). As a result, the measurement result of the adhesiveness was 100/100, indicating that the adhesiveness was good.

(Orientation evaluation)
The orientation of this optical film was evaluated. The orientation was evaluated by rotating the sample under a polarizing plate crossed Nicols and confirming that the dark state did not change to the bright state due to the in-plane retardation. As a result, even when the sample was rotated, the sample was always in a dark state, and the orientation was good (◎).

[Example 2]
(Preparation of optical film)
A coating comprising the prepared polymerizable liquid crystal composition in the same manner as in Example 1, except that a polymerizable liquid crystal composition was prepared using a mixed solvent of MIBK: CPME = 74: 26 as an organic solvent. The liquid was applied on a substrate, dried and cured to produce an optical film.

(STEM observation)
FIG. 8 is an observation image (magnification: 50,000) obtained by observing a cross section of the obtained optical film by STEM. Note that the observation image in FIG. 8 is the same as the observation image in FIG. As can be seen from this observation image, it can be seen that a penetrating layer is formed between the substrate made of polycarbonate and the liquid crystal layer.

(Adhesion evaluation)
The optical film was evaluated for adhesion between the substrate and the liquid crystal layer. The evaluation of adhesion was performed in the same manner as in Example 1. As a result, the measurement result of the adhesiveness was 95/100, which indicates that the adhesiveness was good.

(Orientation evaluation)
The orientation of this optical film was evaluated. The evaluation of the orientation was performed in the same manner as in Example 1. As a result, schlieren defects were observed, and the orientation was slightly inferior to that of Example 1. However, even when the sample under the polarizing plate crossed Nicols was rotated, the sample was always in a dark state, indicating good orientation (O). .

[Comparative Example 1]
A coating comprising the prepared polymerizable liquid crystal composition in the same manner as in Example 1, except that the polymerizable liquid crystal composition was prepared using a mixed solvent of MIBK: MEK = 74: 26 as the organic solvent. The liquid was applied on a substrate, dried and cured to produce an optical film.

(STEM observation)
FIG. 9 is an observation image (magnification: 50,000) obtained by observing a cross section of the obtained optical film by STEM. As can be seen from this observation image, it was not confirmed that a clear permeable layer was formed between the substrate made of polycarbonate and the liquid crystal layer, and a component considered as a dissolved component of the polycarbonate in the liquid crystal layer was not found. The state of floating was confirmed.

(Adhesion evaluation)
This optical film was evaluated for the adhesion between the substrate and the liquid crystal layer. The evaluation of adhesion was performed in the same manner as in Example 1. As a result, the measurement result of the adhesiveness was 100/100, indicating that the adhesiveness was good.

(Orientation evaluation)
On the other hand, when the orientation of this optical film was evaluated in the same manner as in Example 1, as a result, the liquid crystal was randomly oriented, and light leakage was confirmed as a whole, so that the liquid crystal was vertically oriented. The orientation was poor (x).

  Table 1 below summarizes the evaluation results of Examples 1, 2 and Comparative Example 1. In the evaluation of the presence or absence of a permeation layer, those in which a permeation layer could be confirmed were marked with “○”, and those in which no permeation layer was confirmed were marked with “x”.

DESCRIPTION OF SYMBOLS 1 Optical film 2 Liquid crystal display device 11, 25A, 25C, 28 Base material 12 Permeation layer 13 Liquid crystal layer 21 Optical function film 22 Backlight 23 Liquid crystal display panel 24 Liquid crystal cell 25 Linear polarizing plate 25B Polarizer 26 Optical compensation layer (+ C plate) )
27 polarizer 30 adhesive layer

Claims (4)

An optical film comprising a polycarbonate having a reverse wavelength dispersion as a substrate,
Lamination in which a permeation layer and a liquid crystal layer formed of a polymerizable liquid crystal composition (excluding those containing an alignment material that contributes to the alignment of the liquid crystal compound) are sequentially stacked on the polycarbonate substrate. Consisting of body,
The liquid crystal layer is a positive C plate;
No alignment film is provided on the laminate,
The optical film, wherein the permeable layer is formed by dissolving a polycarbonate constituting the base material with a solvent contained in the polymerizable liquid crystal composition. The optical film according to claim 1, wherein the liquid crystal layer does not contain a component dissolved by the solvent of the polycarbonate. As the solvent,
The evaporation rate ratio of the butyl acetate to the evaporation rate is 1 or more and 3 or less, and
The optical film according to claim 1, further comprising a solvent having a time required for dissolving the test piece (2 × 2 cm) of the polycarbonate substrate to be 20 minutes or less as a main component. The optical film according to claim 3, wherein the solvent contains methyl isobutyl ketone (MIBK) as a main component.