JP2013047758A - Optical film laminate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce in thickness an optical film laminate comprising a positive C-plate and an O-plate.SOLUTION: There is provided an optical film laminate in which a positive C-plate (a homeotropic alignment layer) comprising a liquid crystalline material having a photosensitive group and an O-plate (an inclined alignment layer) comprising a liquid crystalline material having a photosensitive group are directly closely adhered and laminated to each other without using an adhesive. A method for manufacturing the laminate includes: coating the homeotropic alignment layer, which is formed of the liquid crystalline material having the photosensitive group and has unfixed alignment, with the liquid crystalline material having the photosensitive group; obliquely irradiating the coating layer with linearly polarized UV rays to form the inclined alignment layer; and subsequently irradiating the layers with non-polarized UV rays to fix the alignment in both layers and to enhance adhesiveness in the interface between the layers.

Description

  The present invention relates to an optical film laminate used for a liquid crystal display device, and more particularly to an optical film laminate having an optical compensation function for improving viewing angle characteristics of a liquid crystal display device and a method for producing the same.

Liquid crystal display devices are required to have a wide viewing angle and high contrast. Examples of such a liquid crystal display device include a liquid crystal display device (LCD) such as an IPS (In-plane Switching: IPS) mode. However, even in such a liquid crystal display device, when the two orthogonal polarizing plates arranged on the front surface and the back surface of the liquid crystal display device are viewed obliquely, the absorption axes of the two polarizing plates appear to deviate from orthogonal. Therefore, there is a problem that light leakage occurs during black display and the contrast is lowered.
From such a problem, in Patent Document 1, the IPS-LCD has positive uniaxial optical anisotropy, and its optical axis extends in a direction perpendicular to the substrate surface (z direction). The first compensation layer (positive C plate) has a positive uniaxial optical anisotropy, and its optical axis extends in a direction parallel to the substrate surface (positive A). A method for improving the viewing angle characteristics depending on the viewing direction by using a plate has been proposed by simulation.

  On the other hand, in the IPS-LCD, provision of a pretilt angle of a liquid crystal material has been proposed from the viewpoint of being advantageous for improving the response speed. In Patent Document 2, in order to improve the viewing angle characteristics in IPS-LCD, a material system in which the pretilt angle is suppressed is used for the liquid crystal material and the alignment film material. In such a material system, the anchoring strength is strong, However, it has been pointed out that the liquid crystal material is difficult to move and the response speed becomes slow. As a solution to such a problem, the pretilt angle of the liquid crystal material is about 5 ° to 10 °. By setting as follows, a method has been proposed in which anchoring to the liquid crystal molecules at the interface of the alignment film is weakened and the electric field response is enhanced.

  Furthermore, a method has been proposed for improving the viewing angle characteristics even when the liquid crystal material has a pretilt angle in the IPS-LCD. According to Non-Patent Document 1, since it is difficult to make the pretilt angle completely 0 ° in the actual IPS manufacturing process, the deterioration of the viewing angle characteristics caused by the generated pretilt angle is positive in the first optical compensation layer. It is proposed by simulation that the C-plate and the second optical compensation layer having positively uniaxial optical anisotropy that is tilted and aligned are improved.

  As a combination of a positive C plate and a tilted alignment layer, a UV curable vertically aligned liquid crystal film as a positive C plate as proposed in the prior art is used, and an electric field, a magnetic field, and an alignment are used as the tilted alignment layer. It is possible to use a liquid crystal film in which the liquid crystal material is tilted or bend-oriented by means of a film or the like and the orientation is fixed. Here, as a means for stacking the positive C plate and the tilted alignment layer and arranging them on the IPS-LCD panel, an adhesive layer or an adhesive layer is filled in the gap between the two optical elements as disclosed in Patent Document 3. A method is mentioned.

JP 11-133408 A JP 2001-228480 A Japanese Patent Laid-Open No. 2005-70097

JOURNAL OF DISPLAY TECHNOLOGY, Volume 2, Issue 3 (September 2006)

  However, in the IPS-LCD, provision of a pretilt angle of the liquid crystal material has been proposed from the viewpoint of being advantageous for improving the response speed, but it occurs from the viewpoint of the pretilt angle of the applied liquid crystal material and the actual process. The deterioration of the viewing angle characteristic due to the pretilt angle of the liquid crystal material cannot be solved by the combination of the positive C plate and the positive A plate proposed in Patent Document 1.

  Further, in the method by setting the pretilt angle of the liquid crystal molecules proposed in Patent Document 2 to about 5 ° or more and 10 ° or less, the contrast is lowered depending on the observation direction, and the cause of the deterioration of the viewing angle characteristic is caused. There is a risk of becoming.

  The combination of the positive C plate and the tilted alignment layer proposed in Non-Patent Document 1 described above is an adhesive for laminating the positive C plate and the tilted alignment layer as disclosed in Patent Document 3. Alternatively, it is necessary to use a pressure-sensitive adhesive, and the thickness of the adhesive layer or the pressure-sensitive adhesive layer is increased. In particular, there is a problem that the LCD panel becomes thick in a portable terminal that is required to be thin. . In addition, in order to bond or stick the positive C plate and the inclined alignment layer, it is indispensable to form an adhesive layer or a pressure-sensitive adhesive layer on at least one of the layers, and further laminate and paste both elements. By adding this process, it becomes easy to produce defective products due to the intervention of foreign matter, and the problem of a decrease in yield arises.

Therefore, the first problem to be solved by the present invention is to further reduce the thickness of the optical compensation film layer composed of the positive C plate and the inclined alignment layer (O plate).
In addition, the second problem to be solved by the present invention is that a liquid crystalline material having a photosensitive group is tilted and aligned on a positive C plate (homeotropic alignment layer) composed of a liquid crystalline material having a photosensitive group. Forming an inclined alignment layer (O plate).
Furthermore, the third problem to be solved by the present invention is a defective product due to foreign matter intervention associated with the use of an adhesive or a pressure-sensitive adhesive in the step of laminating a positive C plate and an inclined alignment layer (O plate). Is to reduce the occurrence rate.

  As a result of diligent research to solve the above problems, the present inventor has found that a liquid crystal material having a photosensitive group is inclined and aligned on a positive C plate composed of a liquid crystal material having a photosensitive group. Layer (O plate) can be formed, and the positive C plate and the O plate can be formed without using an adhesive or an adhesive (hereinafter, the adhesive and the adhesive are collectively referred to as an adhesive and an adhesive). In other words, the present invention has been completed.

The first configuration of the present invention that solves the first problem is a positive C plate made of a liquid crystalline material having a photosensitive group, an O plate made of a liquid crystalline material having a photosensitive group, In the laminated optical film,
The optical film laminate, wherein the positive C plate and the O plate are laminated in direct contact without using an adhesive.

  The positive C plate is preferably composed of a homeotropic alignment layer, and the O plate is preferably composed of a tilted alignment layer.

  The second configuration of the present invention that solves the above second problem is that a photosensitive layer on a positive C plate made of a homeotropic alignment layer (layer A) formed of a liquid crystalline material (material a) having a photosensitive group is exposed. A solution in which a liquid crystalline material having a functional group (material b) is dissolved is applied and dried to form a layer, and then an O plate composed of a tilted alignment layer (layer B) is formed by obliquely irradiating linearly polarized ultraviolet rays. This is a method for producing an optical film laminate.

  In the above production method, it is preferable to form a layer by applying and drying a solution in which the material a is dissolved on a support to form a layer, and then heating to form the layer A, and a layer formed from the material b. It is preferable to form the layer B by obliquely irradiating with linearly polarized ultraviolet rays and then heating.

  The third configuration of the present invention that solves the third problem described above is a positive structure formed of a homeotropic alignment layer (layer A) that is formed of a liquid crystalline material (material a) having a photosensitive group and is not fixed in alignment. On the C plate, an O plate composed of a tilted alignment layer (layer B) formed of a liquid crystalline material having a photosensitive group (material b) is formed, and then a non-polarized light is formed on the laminate of layer A and layer B. An optical film laminate characterized by fixing the alignment in the layer A and the layer B by irradiating a characteristic ultraviolet ray, and laminating both alignment layers in direct contact without using an adhesive. It is a manufacturing method.

  In the above production method, the photosensitive group of the material a and the photosensitive group of the material b are preferably photosensitive groups that react with each other by light, and the photosensitive group of the liquid crystal material a and the material b More preferably, the photosensitive group is the same.

  According to the first configuration of the present invention, since the optical film laminate is obtained in which the positive C plate and the O plate are laminated in direct contact with each other without using an adhesive, the optical film laminate is obtained. Can be used as a thinned optical compensation film. Since the positive C plate and the O plate are in close contact with each other, the optical compensation film has high durability used for a portable terminal or the like without peeling between the two plates.

According to the second configuration of the present invention, on the homeotropic alignment layer (positive C plate) made of a liquid crystalline material having a photosensitive group, a tilted alignment layer (made of a liquid crystalline material having a photosensitive group) ( O plate) can be formed, so that the deterioration of the viewing angle characteristics due to the pretilt angle of the liquid crystal material, which cannot be solved by the combination of the positive C plate and the positive A plate proposed in Patent Document 1, is prevented. be able to.

  According to the third configuration of the present invention, the inclined alignment layer (O plate) is in close contact with the homeotropic alignment layer (positive C plate) without using an adhesive, and it is difficult to cause separation between the two layers. Since a film laminate is obtained, a thin liquid crystal display device can be obtained. In addition, the formation of both the homeotropic alignment layer and the gradient alignment layer can be carried out in a series of steps, and since lamination is performed without using an adhesive, there is no mixing of foreign substances that easily adhere to the adhesive application surface. It is possible to set up an efficient production line with a low incidence of defective products.

  In the present invention, when the photosensitive group of the material a and the photosensitive group of the material b are photosensitive groups that react with each other by light, more preferably, the photosensitive group of the material a and the photosensitive group of the material b Are the same, the photosensitive groups of the material a and the material b can be easily bonded by photoreaction at the interface between the layer A and the layer B constituting both plates, and a stronger adhesion structure can be obtained. It is considered possible.

It is a schematic diagram which shows an example of the optical film laminated body of this invention.

(Basic structure of optical film laminate)
The optical film laminate of the present invention is composed of a laminate of a positive C plate and an O plate.
In the present invention, the positive C plate means that the in-plane main refractive index is nx (slow axis direction), ny (fast axis direction), and the refractive index distribution in the thickness direction is nz. A positive uniaxial retardation optical element satisfying> nx = ny. Such a positive C plate is composed of a homeotropic alignment layer formed from a liquid crystalline material having a photosensitive group.
In the present invention, the O-plate means that the optical axis direction is inclined when viewed from the in-plane direction and the Z-axis direction (thickness direction perpendicular to the in-plane direction). Such an O plate is made of a liquid crystalline material having a photosensitive group, and is usually composed of a tilted alignment layer in which the optical axis of the liquid crystal is tilted.
In the present invention, the positive C plate and the O plate are directly laminated without using an adhesive, and delamination does not occur. By forming the positive C plate and the O plate by the specific method disclosed below, an optical film laminate without delamination can be obtained without using an adhesive.

  FIG. 1 is a schematic view showing an example of the optical film laminate of the present invention. In the optical film laminate 1 of the present invention, a positive C plate (homeotropic alignment layer) 2 and an O plate (gradient alignment layer) 3 are directly laminated at the interface 4 without an adhesive.

(Positive C plate)
In the present invention, the positive C plate is composed of a homeotropic alignment layer formed from a liquid crystalline material having a photosensitive group. Here, homeotropic alignment refers to a state in which the liquid crystalline material is aligned in parallel and uniformly with respect to the film normal direction, that is, a state in which the liquid crystal material is aligned vertically. The liquid crystalline material capable of homeotropic alignment may be a liquid crystalline polymer or a liquid crystalline monomer.

(O plate)
In the present invention, the O plate is a liquid crystal material formed from a liquid crystal material having a photosensitive group and arranged obliquely with respect to the film plane (the inclination angle is larger than 0 ° and smaller than 90 °). This means an inclined alignment layer. The O plate may be a uniaxial or biaxial birefringent material (however, the largest axis of the refractive index ellipsoid is not in the film plane and in the normal direction).
The liquid crystalline material that can be tilted may be a liquid crystalline polymer or a liquid crystalline monomer.

(Liquid crystalline material having photosensitive group)
In the present invention, the liquid crystalline material having a photosensitive group used for forming a positive C plate (homeotropic alignment layer) and an O plate (tilted alignment layer) includes (i) cinnamoyl group, chalcone group, Biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are frequently used as mesogenic components of liquid crystalline polymers, and photosensitive groups such as DENKI, biphenylacryloyl, furylacryloyl, naphthylacryloyl (or their derivatives) And a photosensitive side chain type liquid crystalline polymer having a side chain including a structure in which a substituent such as is bonded via a spacer or not. In addition, it has a photosensitive side chain having a carboxyl group at the end of the side chain, forms a rigid structure by dimerization of the carboxyl group at the end of the side chain by hydrogen bonding, and includes a mesogenic group in the side chain itself Polymers that exhibit liquid crystal properties are also preferably used in the present invention. Examples of the main chain constituting the photosensitive side chain type liquid crystalline polymer include hydrocarbons, acrylates, methacrylates, siloxanes, maleimides, N-phenylmaleimides, and the like in which the side chains are bonded via a spacer. . These polymers are a single polymer composed of the same repeating unit, a copolymer composed of a plurality of units having side chains with different structures, or a unit having a side chain containing a photosensitive group and a side not containing a photosensitive group. Any of the copolymers obtained by blending the unit having a chain to such an extent that the liquid crystallinity is not impaired may be used. In the present invention, the photosensitive group refers to a functional group that binds to other molecules by light irradiation. In the present invention, the liquid crystalline material indicates liquid crystallinity when a physical external stimulus (heating, cooling, electric field, magnetic field, application of shear, etc.) is given to the material alone, or a solvent or non-liquid crystalline property. A material that exhibits liquid crystallinity when mixed with a component.
Furthermore, in order to improve heat resistance, a polymer in which a reactive group is introduced into the above polymer and a crosslinking structure is introduced to the extent that liquid crystallinity is not impaired by a crosslinking agent such as an isocyanate material or an epoxy material may be used. Further, a bifunctional low molecular material may be added as the following low molecular material for polymerization to contain a crosslinkable polymer.

(Formation of homeotropic alignment layer and inclined alignment layer)
In the present invention, the homeotropic alignment layer is a film formed from a solution obtained by dissolving the above-described liquid crystalline material (liquid crystalline polymer), preferably a liquid crystalline material (liquid crystalline polymer) represented by the following chemical formulas 1 to 3 in a solvent. Can be formed by heating after removing the solvent.
In the present invention, the tilted alignment layer is formed by forming a film from a solution obtained by dissolving the above-described liquid crystalline material (liquid crystalline polymer) in which a low molecular compound described below is added, if necessary, in a solvent. After removal, it can be formed by obliquely irradiating and heating linearly polarized ultraviolet rays.
The homeotropic alignment layer and the inclined alignment layer formed as described above can be fixed in their respective alignments by further irradiating non-polarizing ultraviolet rays.

(Formation of laminate)
The optical film laminate of the present invention first forms a homeotropic alignment layer by the above method, and then forms a tilt alignment layer directly on the formed homeotropic alignment layer by the above method, or First, a tilted alignment layer is formed, and then a homeotropic alignment layer is formed on the tilted alignment layer. By this, the optical film laminated body which consists of a homeotropic alignment layer and an inclination alignment layer can be formed, without passing through an adhesive agent. Hereinafter, in this specification, a case where a homeotropic alignment layer is first formed and then a tilted alignment layer is specifically described.

(Polymer forming homeotropic alignment layer)
The polymer used for forming the homeotropic alignment layer in the present invention is preferably a polymer formed using a monomer having a side chain represented by the following chemical formula 1, 2 or 3.

In the formulas of [Chemical Formula 1] and [Chemical Formula 2], n represents 1 to 12, m represents an integer of 1 to 12, and X or Y represents none, —COO, —OCO—, —N═. N—, —C═C— or —C ₆ H ₄ —, respectively, and W ₁ represents a cinnamoyl group, a chalcone group, a cinnamylidene group, a biphenylacryloyl group, a furylacryloyl group, a naphthylacryloyl group or a derivative thereof. carded or,, -H, -OH, or represents -CN, W ₂ is a cinnamoyl group, a chalcone group, Shin'namiridenki group, biphenyl acryloyl group, a furyl acryloyl group, naphthyl acrylate or represents acryloyl group or a derivative thereof, Or, -H, -OH or -CN is represented.

Among the side chains represented by the above formula, a monomer having a side chain in which W ₁ and W ₂ are represented by —H, —OH or —CN does not exhibit photosensitivity, but when this material is used, By copolymerizing with a monomer having a photosensitive group in the side chain, a liquid crystalline polymer having a photosensitive group used in the present invention can be obtained. In the case of copolymerization, the higher the proportion of the monomer that does not exhibit photosensitivity represented by the above formula, the easier it is to obtain a polymer that is more likely to be homeotropically oriented. However, the copolymerization proportion is a balance between homeotropic orientation and liquid crystallinity. Can be set as appropriate. In this case, as the liquid crystalline monomer having a photosensitive group in the side chain, a homeotropic alignment layer may be used which has the same or similar chemical structure as the liquid crystalline monomer used to form the later-described tilted alignment layer. It is preferable at the point which raises the close_contact | adherence in the interface of an inclination orientation layer.

In the formula of [Chemical Formula 3], s represents 0 or 1, t represents an integer of 1 to 3, and R represents H, an alkyl group, an alkyloxy group, or a halogen.

  A liquid crystalline polymer formed from the monomer unit having a side chain represented by the above chemical formulas 1-3, and if necessary, a low molecular compound and other components (such as a polymerization catalyst) are added to the above liquid crystalline polymer, and these are appropriately used. A liquid crystal polymer layer can be formed on a support by applying a coating solution prepared by dissolving in a solvent to the support and removing the solvent.

  Examples of the solvent include dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, and the like, and these solvents are used alone or in combination. In the process of applying the coating liquid on the support and removing the solvent, the formed layer starts to exhibit homeotropic alignment, and after drying, the homeotropic alignment is enhanced by further heating. Drying may be performed at room temperature, or may be performed by heating to a temperature below the isotropic phase transition temperature of the material. Depending on the material, homeotropic orientation may be exhibited on the surface of the support film.

  The support is appropriately selected from various polymer films. For example, polyethylene terephthalate film, cellulose polymer film such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymer film such as bisphenol A / carbonic acid copolymer, linear or branched such as polyethylene, polypropylene and ethylene / propylene copolymer For example, a polyolefin film, a polyamide film, an imide polymer film, and a sulfone polymer film.

  Spin coating or roll coating so that a solution of a liquid crystalline polymer containing a polymerizable unit having a side chain represented by the above chemical formulas 1 to 3 is dissolved in the above solvent into a film having a predetermined thickness on the above support. Apply by an application method such as screen printing, knife coating, spray coating, etc., and after application, dry to remove the solvent, and further heat to 80 to 130 ° C., preferably 100 to 120 ° C., and then cool. Thus, a homeotropic alignment layer can be formed. Even if the homeotropic alignment layer formed as described above is irradiated with polarizing ultraviolet rays, the homeotropic alignment can be maintained with little influence on the alignment. The homeotropic alignment layer formed in this way can fix the alignment by irradiating non-polarizing ultraviolet rays, but in the present invention, after laminating the inclined alignment layer, as will be described later. It is necessary to do so when laminating the homeotropic alignment layer and the gradient alignment layer without using an adhesive.

(Formation of inclined alignment layer)
On the homeotropic alignment layer formed as described above, a liquid crystalline polymer containing a unit having a side chain represented by the above formulas 1 to 3, preferably a liquid crystalline polymer in which the above homeotropic layer is formed Using the same liquid crystalline polymer, a liquid crystalline polymer solution obtained by dissolving the same in a solvent is applied on the homeotropic alignment layer, dried after coating, and obliquely irradiated with linearly polarized ultraviolet rays without heating after drying. By heating, the liquid crystalline polymer forms an inclined alignment layer, and this alignment can be fixed by irradiating non-polarizing ultraviolet rays.

Further, on the homeotropic alignment layer formed as described above, an inclined alignment layer is formed from the liquid crystalline polymer different from the polymerizable monomer having a side chain represented by the above formulas 1 to 3 by the above method. can do.
As the liquid crystalline polymer for forming such a tilted alignment layer, the present applicant discloses in JP-A-11-189665, JP-A-2002-202409, JP-A-2004-170595, JP-A-2005-232345, and the like. The liquid crystalline polymer can be used, but in particular, it is possible to obtain the adhesion at the interface between the two layers by selecting one having a high chemical structural similarity to the liquid crystalline polymer forming the homeotropic alignment layer. It is preferable from the point of being easy. For example, when the photosensitive group of the liquid crystal polymer forming the homeotropic alignment layer and the photosensitive group of the liquid crystal polymer forming the tilted alignment layer are cinnamoyl groups, the respective double bonds of the pair of cinnamoyl groups are opened. Since a cyclobutane bond can be formed (see the following chemical formula 4), it is considered that dimerization occurs at the interface between both layers due to a similar reaction, and strong adhesion can be obtained at the interface.

(Low molecular material)
In the present invention, in order to enhance the alignment in the tilted alignment layer, the liquid crystalline polymer having the photosensitive group is mixed with a low molecular material, and the mixture is obliquely irradiated with linearly polarized ultraviolet rays. Is preferably formed. Such low molecular weight materials include substituents such as biphenyl, terphenyl, phenylbenzoate and azobenzene, which are known as mesogenic components, and such substituents and allyl, acrylate, methacrylate, cinnamic acid groups (or derivatives thereof) A group having a liquid crystallinity in which a functional group such as a group is bonded via a bending component as described above is preferably used. These low molecular materials are not only used as a single material, but a plurality of materials may be mixed. Such a low molecular weight material is preferably added in a range of 5 to 50% by weight, preferably 10 to 30% by weight, based on the liquid crystalline polymer. Benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4, Photosensitizers such as 4′-bis (dimethylamino) benzophenone and benzophenone derivatives such as 4,4′-bis (diethylamino) benzophenone are preferably added.

(Diagonal irradiation of linearly polarized UV light)
Prepared by dissolving a liquid crystalline polymer having a photosensitive group or a mixture of the above polymer with a low molecular weight material in a solvent such as dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone. The obtained solution is applied and dried on the homeotropic alignment layer to form a film. The drying in this case may be performed at room temperature, or may be performed by heating at a low temperature of, for example, 60 ° C. or less, depending on the material. If the temperature is raised too much, the formed film may become cloudy.
Subsequently, linearly polarized ultraviolet rays are obliquely irradiated to the formed film. As an ultraviolet ray source, a mercury excitation light source such as a low pressure mercury lamp, a medium pressure mercury lamp, or a high pressure mercury lamp, or a xenon light source is used, and linearly polarized light can be obtained by passing light from the light source through a polarizing filter or a polarizing prism. it can. In the present invention, in order to irradiate ultraviolet rays obliquely, the irradiated film is inclined in the range of 0 <X <85 ° with respect to the horizontal plane with respect to the ultraviolet ray source arranged in the normal direction to the horizontal plane. Preferably, the irradiation is performed, and it is more preferable to perform the irradiation while inclining in the range of 5 <X <60 °. By irradiating in such a manner, a tilted alignment layer in which the optical axis is tilted so that the optical axis is 0 <Y <45 °, preferably 2 <Y <40 °, can be obtained. The degree of tilt orientation is selected according to the desired degree of light compensation.
In order to advance this photoreaction, it is necessary to irradiate light having a wavelength at which the photosensitive group portion can react. Although it varies depending on the type of the side chain, it is generally 200-500 nm, and in particular, the effectiveness of 250-400 nm is often high. Even when such linearly polarized ultraviolet rays are obliquely irradiated, the orientation of the homeotropic alignment layer is not substantially affected.

(Heating after oblique irradiation of linearly polarized UV light)
After oblique irradiation with polarizing UV rays, the polymer side chains and low molecular weight materials that have not undergone photoreaction are reoriented in the same direction as the photoreacted side chains due to molecular motion within the film by heating the film. To do. As a result, in the entire film, the side chains of the polymer and the molecules of the low molecular material are aligned in the direction of the electric field vibration of the linearly polarized light that is obliquely irradiated and the direction perpendicular to the traveling direction of the irradiation light, and birefringence is induced to induce the inclined alignment layer It becomes. Heating after irradiation with polarizing UV light promotes this reorientation. The heating temperature is preferably set to be equal to or lower than the isotropic phase transition temperature of the material of the homeotropic layer.
When the film thus exposed and heated to align the unreacted side chain or the film exposed and aligned under heating is cooled below the softening point of the polymer, the molecules are frozen and a tilted alignment layer is obtained. . Cooling is preferably performed by ordinary standing cooling. If rapid cooling is performed, reorientation may be insufficient.

(Non-polarizing UV irradiation)
Next, it is preferable to irradiate the tilted alignment layer with non-polarizing ultraviolet rays. When irradiated with non-polarizing ultraviolet light, the liquid crystalline polymer having unreacted photosensitive groups remaining in the film reacts to fix the orientation, and a stable tilted orientation layer is formed, and the homeotropic orientation layer The orientation at is also fixed. In addition, at the interface between the homeotropic alignment layer and the gradient alignment layer, a photoreaction occurs between the photosensitive groups of the liquid crystalline polymer forming each layer, which contributes to high adhesion between the two layers. It is done. In addition, although irradiation with non-polarizing ultraviolet rays is usually performed without heating, when it is necessary to adjust (decrease) the retardation value, it can also be performed with heating.

  As described above, the optical film laminate of the present invention can be formed by forming the inclined alignment layer directly on the homeotropic alignment layer without using an adhesive. The optical film laminate formed on the support can be separated from the support film by transferring the adhesive onto the polarizing plate or the liquid crystal cell constituting the liquid crystal panel. .

(Homeotropic alignment layer and gradient alignment layer thickness)
The thickness of the homeotropic alignment layer and the inclined alignment layer is preferably 0.3 to 3 μm, and more preferably 0.5 to 2.5 μm.
According to the present invention, an optical film laminate composed of a homeotropic alignment layer and a tilt alignment layer can be formed very thin as 0.6 to 6 μm, and therefore an optical compensation film (used for a conventional liquid crystal display device ( The display device can be made thinner as compared with a thin film having a thickness of 15 μm.

  From the point of peel resistance of the optical film laminate according to the present invention, the photosensitive group of the photosensitive liquid crystalline polymer that forms the homeotropic alignment layer and the photosensitive group of the liquid crystalline polymer that forms the tilted alignment layer are included. It is preferable that the photosensitive groups react with each other by light, and that both the photosensitive groups are the same, the polymer photosensitivity that is contacted by ultraviolet irradiation at the interface between the homeotropic alignment layer and the tilted alignment layer. It is preferable because the adhesiveness is enhanced by the chemical bonding between the groups. Among the above-described photosensitive groups, cinnamoyl group, chalcone group, cinnamylidene group photosensitive groups, and photosensitive groups having an acryloyl group such as biphenylacryloyl are photosensitive groups that react with each other.

(Display device)
The optical film laminate according to the present invention is used as a liquid crystal display panel in combination with a polarizing plate. Especially, it is effective as a liquid crystal display panel of a portable terminal or the like that is strongly required to be thin.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples. A synthesis method relating to the materials used in the examples of the present invention will be described below. Further, whether the sample obtained in the example of the present invention was a positive C plate or an O plate was determined as follows.

(Monomer 1)
4-Hydroxy-4'-hydroxyethoxybiphenyl was synthesized by heating 4,4'-biphenyldiol and 2-chloroethanol under alkaline conditions. This product was reacted with 1,6-dibromohexane under alkaline conditions to synthesize 4- (6-bromohexyloxy) -4′-hydroxyethoxybiphenyl. Next, lithium methacrylate was reacted to synthesize monomer 1 represented by Chemical Formula 5.

(Monomer 2)
Cinnamoyl chloride was added to monomer 1 under basic conditions to synthesize monomer 2 represented by chemical formula 6.

(Low molecular material 1)
4,4′-biphenyldiol and 6-bromohexanol were reacted under alkaline conditions to synthesize 4,4′-bis (6-bromohexyloxy) biphenyl. Next, methacrylic acid chloride was added and reacted under basic conditions, and the product was recrystallized to synthesize a low molecular weight material 1 represented by Chemical Formula 7.

(Polymer 1)
Monomer 1 and monomer 2 are dissolved in tetrahydrofuran at a molar ratio of 3: 7, AIBN (azobisisobutyronitrile) is added as a reaction initiator, and polymerization is performed at 70 ° C. for 24 hours. Polymer 1 was obtained. This polymer 1 exhibited liquid crystallinity.

(Polymer 2)
Monomer 2 was dissolved in tetrahydrofuran, AIBN (azobisisobutyronitrile) was added as a reaction initiator, and polymerization was conducted at 70 ° C. for 24 hours to obtain photosensitive polymer 2. This polymer 2 exhibited liquid crystallinity.

(Positive C plate, O plate determination method)
Using an automatic birefringence meter, the angle dependency of the phase difference value was determined by the crystal rotation method, and the determination was made based on the angle dependency.

[Example 1]
Polymer 1 was dissolved in cyclohexanone, and 0.02 part by weight of commercially available (Tokyo Kasei) 4,4′-bis (diethylamino) benzophenone was added to Polymer 1 to prepare Solution 1. This solution was applied on a polyethylene terephthalate film (PET film) to a thickness of about 1.5 μm using a spin coater. This substrate was dried at room temperature (about 25 ° C.), then heated to 100 ° C. and then cooled to form a first coating film. Next, 4.2% by weight of the polymer 2 and 0.8% by weight of the low molecular weight material 1 are dissolved in toluene, and 0.02 part by weight of the total weight of the polymer 2 and the low molecular weight material 1 is dissolved therein. Commercially available [manufactured by Tokyo Chemical Industry Co., Ltd.] 4,4′-bis (diethylamino) benzophenone was added to prepare Solution 2. The solution 2 was applied onto the first coating film using a spin coater so as to have a thickness of about 1.8 μm, and dried to form a second coating film on the first coating film. Here, the second coating film was formed on the first coating film without irradiating the first coating film with ultraviolet rays and without fixing the orientation (the photosensitive group remained unreacted).

  Subsequently, this coating film was tilted by 20 ° with respect to the horizontal plane, and light from the high-pressure mercury lamp was made linearly polarized by using a Granteller prism and irradiated to the horizontal plane for 300 seconds from the normal direction (the electric field vibration surface of the light was Orthogonal to the film tilt axis). Subsequently, after heating at 100 ° C., it was gradually cooled to room temperature over 30 minutes to induce orientation. Furthermore, in order to fix the orientation, light from a high-pressure mercury lamp was irradiated for 1500 seconds without being converted into linearly polarized light.

  The coating film thus produced could be transferred from a PET support to a liquid crystal cell or a polarizing plate using an adhesive. Further, it was confirmed that the optical properties were optical properties composed of a laminate of a positive C plate (homeotropic alignment layer) and an inclined alignment layer (O plate) (inclination angle: 10 °). Furthermore, in order to confirm the adhesion at the coating film interface between the first coating film and the second coating film, peeling at the coating film interface was attempted using cello tape (registered trademark). Was not observed, and it was confirmed to have good adhesion.

[Example 2]
Polymer 1 was dissolved in cyclohexanone, and 0.02 part by weight of commercially available (Tokyo Kasei) 4,4′-bis (diethylamino) benzophenone was added to Polymer 1 to prepare Solution 1. This solution was applied on a polyethylene terephthalate film (PET film) to a thickness of about 1.5 μm using a spin coater. The substrate was dried at room temperature (about 25 ° C.), then heated to 100 ° C. and then cooled for 30 minutes. Subsequently, the light from the high pressure mercury lamp was irradiated for 1500 seconds without being converted into linearly polarized light, the orientation was fixed, and a first coating film (homeotropic orientation layer) was formed. Next, 4.2% by weight of the polymer 2 and 0.8% by weight of the low molecular weight material 1 are dissolved in toluene, and 0.02 part by weight of the total weight of the polymer 2 and the low molecular weight material 1 is dissolved therein. Commercially available (Tokyo Kasei) 4,4′-bis (diethylamino) benzophenone was added to prepare Solution 2. The solution 2 was applied onto the first coating film using a spin coater so as to have a thickness of about 1.8 μm, and dried to form a second coating film on the first coating film.

  Subsequently, this coating film was tilted by 20 ° with respect to the horizontal plane, and light from the high-pressure mercury lamp was made linearly polarized by using a Granteller prism and irradiated to the horizontal plane for 300 seconds from the normal direction (the electric field vibration surface of the light was Orthogonal to the film tilt axis). Subsequently, after heating at 100 ° C., it was gradually cooled to room temperature over 30 minutes to induce orientation. Furthermore, in order to fix the orientation, light from a high-pressure mercury lamp was irradiated for 1500 seconds without being converted into linearly polarized light.

The coating film thus produced could be transferred from a PET substrate to a liquid crystal cell and a polarizing plate using an adhesive. Moreover, it was confirmed that the optical characteristic has the optical characteristic which consists of a laminated body of positive C plate and O plate.
However, in order to confirm the adhesion at the coating film interface between the first coating film and the second coating film, when peeling at the coating film interface was attempted using cello tape (registered trademark), compared to Example 1. It was easy to peel off and was insufficient in terms of adhesion.

  As described above, according to the optical film laminate of the present invention, a thin optical film having an optical compensation function can be obtained, which can contribute to a thin liquid crystal display device. The liquid crystal panel of the present invention is suitably used for a liquid crystal display device such as a portable terminal.

  As described above, the preferred embodiments of the present invention have been described with reference to the drawings, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention. Included in the range.

1: Optical film laminate 2: Positive C plate 3: Inclined alignment layer 4: Interface

Claims (10)

A positive C plate composed of a liquid crystalline material having a photosensitive group;
In an optical film laminate in which an O plate composed of a liquid crystalline material having a photosensitive group is laminated,
The optical film laminate, wherein the positive C plate and the O plate are directly adhered and laminated without using an adhesive.   The optical film laminate according to claim 1, wherein the positive C plate is composed of a homeotropic alignment layer.   The optical film laminate according to claim 1, wherein the O plate is composed of a tilted alignment layer.   4. The optical film stack according to claim 1, wherein the O plate is a uniaxial or biaxial birefringent material (however, the largest axis of the refractive index ellipsoid is not in the film plane and in the normal direction). body.   A solution in which a liquid crystalline material having a photosensitive group (material b) is dissolved is applied onto a positive C plate composed of a homeotropic alignment layer (layer A) formed from a liquid crystalline material having a photosensitive group (material a). A method for producing an optical film film laminate, comprising forming a layer by drying, and then forming an O plate composed of a tilted alignment layer (layer B) by obliquely irradiating linearly polarized ultraviolet rays.   The method for producing an optical film laminate according to claim 5, wherein the solution in which the material a is dissolved is applied to a support and dried to form a layer, and then the layer A is formed by heating.   The method for producing an optical film laminate according to claim 5 or 6, wherein the layer formed from the material b is obliquely irradiated with linearly polarized ultraviolet rays and then heated to form the layer B.   A liquid crystalline material having a photosensitive group (material b) on a positive C plate formed of a homeotropic alignment layer (layer A) which is formed of a liquid crystalline material having a photosensitive group (material a) and which is not fixed in alignment. The layer A and the layer B are irradiated with non-polarizing ultraviolet rays, and then an O-plate composed of a tilted alignment layer (layer B) formed from A method for producing an optical film laminate comprising fixing an orientation and laminating both orientation layers in direct contact without using an adhesive.   9. The method for producing an optical film laminate according to claim 8, wherein the photosensitive group of the material a and the photosensitive group of the material b are photosensitive groups that react with each other by light.   The method for producing an optical film laminate according to claim 9, wherein the photosensitive group of the liquid crystalline material a and the photosensitive group of the material b are the same.

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