JP7806475B2 - Liquid crystal device - Google Patents

Description

Embodiments of the present disclosure relate to liquid crystal devices.

Conventionally, liquid crystal devices such as dimming components using liquid crystals and dimming devices using such dimming components have been proposed, which can be used in combination with light-transmitting components such as windows to control the transmission of external light, and which can be used in electronic blinds and other applications (see, for example, Patent Document 1).

International Publication No. 2019/198748

Such liquid crystal devices are configured with a pair of glass plates, a liquid crystal cell placed between the glass plates, and a bonding layer provided between each glass plate and the liquid crystal cell.

However, when a completed liquid crystal device is exposed to a high-temperature environment, the base material of the liquid crystal cell and the liquid crystal expand, while the bonding layer made of conventional PVB softens. As a result, the positional control force of the bonding layer that maintains the shape of the liquid crystal cell weakens, and liquid crystal accumulation, a phenomenon in which the liquid crystal in the liquid crystal cell is locally unevenly distributed, can occur, resulting in liquid crystal unevenness.
The unevenness in the liquid crystal is easily visible to the naked eye, and is not preferable because it impairs the appearance of the liquid crystal device and also reduces the performance of the liquid crystal cell.

The objective of the embodiments of the present disclosure is to provide a liquid crystal device that can suppress the occurrence of liquid crystal unevenness even when exposed to a high-temperature environment.

The embodiments of the present disclosure solve the above-mentioned problems by the following solutions. Note that, for ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present disclosure, but the present disclosure is not limited to these.
A first disclosed embodiment is a liquid crystal device (1) comprising a first transparent substrate (41), a second transparent substrate (42), a liquid crystal cell (10) arranged between the first transparent substrate and the second transparent substrate, a first bonding layer (31) arranged between the first transparent substrate and the liquid crystal cell, and a second bonding layer (32) arranged between the second transparent substrate and the liquid crystal cell, wherein at least one of the first transparent substrate or the second transparent substrate has a curved shape that is convex toward the liquid crystal cell along at least one direction parallel to a surface of the liquid crystal device, and in a cross section passing through a center (P1) of the liquid crystal cell in a plan view of the liquid crystal device and parallel to the one direction, a thickness (T1) of the first bonding layer at the center of the liquid crystal cell is smaller than a thickness (T2) of the first bonding layer at an outer peripheral edge (P2) of the liquid crystal cell.
A second disclosed embodiment is a liquid crystal device (1) according to the first disclosed embodiment, wherein the first bonding layer (31) is made of OCR, and a ratio T/W of a difference T between a thickness (T1) of the first bonding layer at a center (P1) of the liquid crystal cell (10) and a thickness (T2) of the first bonding layer at an outer peripheral edge (P2) of the liquid crystal cell, to a distance W between the center of the liquid crystal cell and the outer peripheral edge of the liquid crystal cell, satisfies T/W>1.0× ^10-3 .
A third disclosed embodiment is a liquid crystal device (1) in which the second bonding layer (32) in the liquid crystal device of the first or second disclosed embodiment is made of OCA.
A fourth disclosed embodiment is a liquid crystal device (1) according to any one of the first to third disclosed embodiments, wherein the first transparent substrate (41) has the curved shape.

According to the embodiments of the present disclosure, it is possible to provide a liquid crystal device that can suppress the occurrence of liquid crystal unevenness even when exposed to a high-temperature environment.

1 is an exploded perspective view showing a configuration of a liquid crystal device 1 according to an embodiment of the present disclosure. 1 is a cross-sectional view showing a layer configuration of a liquid crystal device 1 according to an embodiment of the present disclosure. 4A and 4B are diagrams illustrating the curved shape of a first glass plate 41 according to an embodiment of the present disclosure. 3A to 3C are cross-sectional views illustrating a method for manufacturing the liquid crystal device 1 according to the embodiment of the present disclosure. 4A and 4B are diagrams illustrating the thickness of a first bonding layer 31 according to an embodiment of the present disclosure. 1 is a plan view illustrating a liquid crystal device 1X of a comparative example exposed to a high-temperature environment. 10A and 10B are diagrams illustrating another embodiment of the liquid crystal device 1.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, etc. Note that the drawings shown below, including Fig. 1, are schematic diagrams, and the size and shape of each part are appropriately exaggerated for ease of understanding.
In the following description, specific numerical values, shapes, materials, etc. are given, but these can be changed as appropriate.
In this specification, terms specifying shapes or geometric conditions, such as parallel and orthogonal, are intended to include not only their strict meanings but also states that perform similar optical functions and have an error that can be considered as parallel or orthogonal.

In this specification, the terms plate, sheet, film, etc. are used, but in general, these are used in order of thickness, that is, plate, sheet, film, and so on, and this specification follows suit. However, since there is no technical significance in this distinction, these terms can be used interchangeably as appropriate.
In this specification, the term "sheet surface" refers to the surface of each sheet that is in the planar direction of the sheet when viewed as a whole. The same applies to the plate surface and film surface. In this specification, the term "planar view" refers to the state when viewed from a direction perpendicular to the main surface of the liquid crystal device.

In this specification, the term "transparent" refers to a material that transmits at least the light of the wavelength to be used. For example, even if a material does not transmit visible light, if it transmits infrared light, it will be treated as transparent when used in infrared applications.
It should be noted that the specific numerical values specified in this specification and claims should be treated as including a general error range. In other words, a difference of about ±10% is not substantially different, and numerical values set in a range slightly exceeding the numerical range of the embodiments of the present disclosure should be interpreted as being substantially within the range of the embodiments of the present disclosure.

(Embodiment)
FIG. 1 is an exploded perspective view showing the configuration of a liquid crystal device 1 according to an embodiment of the present disclosure.
FIG. 2 is a cross-sectional view showing the layer structure of the liquid crystal device 1 according to the embodiment of the present disclosure.
The liquid crystal device 1 according to the embodiment of the present disclosure can be applied to various technical fields requiring adjustment of light transmittance, and the scope of application is not particularly limited. The liquid crystal device 1 is disposed in a portion where light control is required, such as a window glass of a building, a showcase, an indoor transparent partition, a vehicle window (e.g., a front, side, rear, or roof window), or a partition board inside a vehicle. This allows the amount of light incident on the inside of a building, vehicle, etc. to be controlled, or the amount of light incident on a predetermined area inside the building, vehicle, etc.

The liquid crystal device 1 according to the embodiment of the present disclosure will be described by taking an example in which the overall shape is a flat plate.
In the embodiment of the present disclosure, an example will be described in which the liquid crystal device 1 has a square shape in a plan view.

A liquid crystal device (laminated glass) 1 according to an embodiment of the present disclosure includes a first glass plate 41, a first bonding layer 31, a liquid crystal cell 10, a second bonding layer 32, and a second glass plate 42. The first glass plate 41, the first bonding layer 31, the liquid crystal cell 10, the second bonding layer 32, and the second glass plate 42 are laminated in this order along the thickness direction of the liquid crystal device 1.
The liquid crystal cell 10 comprises a first laminate 12 including a first substrate 21A, a first transparent electrode 22A, and a first alignment layer 23A, a second laminate 13 including a second substrate 21B, a second transparent electrode 22B, and a second alignment layer 23B, and a liquid crystal layer 14 disposed between the first laminate 12 and the second laminate 13.

The first glass plate (first transparent substrate) 41 and the second glass plate (second transparent substrate) 42 are disposed on the front and rear surfaces of the liquid crystal device 1, respectively, and are plate glasses having high light transmittance.
In an embodiment of the present disclosure, the first glass plate 41 and the second glass plate 42 have a thickness of 0.5 mm to 4 mm, and as an example, each is made of a 2 mm thick plate glass. When inorganic glass is used as the first glass plate 41 and the second glass plate 42, the liquid crystal device 1 can have excellent heat resistance and scratch resistance. The first glass plate 41 and the second glass plate 42 may be subjected to a surface treatment such as a hard coat, as necessary.

Instead of the first glass plate 41 and the second glass plate 42 made of inorganic glass, transparent resin plates (so-called resin glass) may be used as the first and second transparent substrates. Examples of such transparent resin plates include polycarbonate and acrylic. Using transparent resin plates as the first and second transparent substrates allows for a reduction in the weight of the liquid crystal device 1.

In the embodiment of the present disclosure, the second glass plate 42 is flat, but the first glass plate 41 is three-dimensionally curved so as to be convex toward the liquid crystal cell 10. The curved shape of the first glass plate 41 does not affect the shape of the liquid crystal device 1, and the liquid crystal device 1 is flat when viewed as a whole. For ease of understanding, in Figures 1, 2, and Figure 4 described below, the curved shape of the first glass plate 41 is omitted and it is shown as a flat plate.

FIG. 3 is a diagram illustrating the curved shape of the first glass plate 41 according to the embodiment of the present disclosure.
In the embodiment of the present disclosure, the curved shape of the first glass plate 41 is, as shown in FIG. 3 , curved so that the plate surface of the first glass plate 41 forms a three-dimensional curved surface when viewed as a whole.
Here, for example, a "two-dimensional curved surface" means a surface that is curved two-dimensionally around a single axis, or a surface that is curved two-dimensionally with different curvatures around multiple axes that are parallel to each other, and a "three-dimensional curved surface" means a surface that is partially or entirely curved around multiple axes that form angles with each other.

In the embodiment of the present disclosure, the surface 41 a of the first glass plate 41 has a three-dimensional curved surface whose geometric center, point C, is the most protruding point. This point C coincides with the geometric center of the liquid crystal cell 10 and the liquid crystal device 1 in a plan view.
The first glass plate 41 is disposed in the liquid crystal device 1 so that the surface 41 a faces the liquid crystal cell 10 .

The first bonding layer 31 is disposed between the first glass plate 41 and the liquid crystal cell 10, and is a member that bonds the first glass plate 41 and the liquid crystal cell 10 to each other.
The first bonding layer 31 is larger in plan view than the liquid crystal cell 10. In addition, the first bonding layer 31 may be the same size as the first glass plate 41 and the second glass plate 42, or may be larger than the liquid crystal cell 10 and smaller than the first glass plate 41 and the second glass plate 42.

As shown in Figure 2, in a cross-sectional view of the liquid crystal device 1, the first bonding layer 31 is formed not only in the area covering the liquid crystal cell 10 but also in the area corresponding to the periphery of the liquid crystal cell 10, and is connected to the second bonding layer 32 in this area.
By forming the first bonding layer 31 in this form, the side surface or a part thereof of the liquid crystal cell 10 is prevented from being exposed on the side surface (end surface) of the liquid crystal device 1, and the intrusion of moisture and the like from the side surface of the liquid crystal device 1 is suppressed, thereby further improving the water-tightness of the liquid crystal device 1.

In an embodiment of the present disclosure, the first bonding layer 31 is composed of OCR (Optical Clear Resin). OCR is a cured product obtained by curing a liquid curable adhesive layer composition containing a polymerizable compound. Specifically, OCR is a liquid resin made by mixing a base resin such as an acrylic resin, silicone resin, or urethane resin with an additive, which is applied to an object and then cured using, for example, ultraviolet (UV) light. The first bonding layer 31 is optically transparent and preferably has heat resistance, moist heat resistance, and weather resistance up to at least approximately 120°C.

The thickness of the first bonding layer 31 may be appropriately selected depending on the material thereof, etc. Specifically, the thickness of the first bonding layer 31 in the region overlapping with the liquid crystal cell 10 in a plan view may be 30 μm or more and 1000 μm or less.
The thickness of the first bonding layer 31 in this embodiment changes in accordance with the curved shape of the first glass plate 41. While satisfying the above-mentioned preferable thickness range, the first bonding layer 31 is thinnest at the center of the liquid crystal cell 10 in a plan view and becomes thicker toward the periphery of the liquid crystal cell 10.

The second bonding layer 32 is disposed between the second glass plate 42 and the liquid crystal cell 10, and is a member that bonds the second glass plate 42 and the liquid crystal cell 10 to each other.
The second bonding layer 32 is larger in plan view than the liquid crystal cell 10. In addition, the second bonding layer 32 may be the same size as the first glass plate 41 and the second glass plate 42, or may be larger than the liquid crystal cell 10 and smaller than the first glass plate 41 and the second glass plate 42.

In the embodiment of the present disclosure, the second bonding layer 32 is made of an optical clear adhesive (OCA). The OCA is a layer produced, for example, as follows.
First, a liquid curable adhesive layer composition containing a polymerizable compound is applied to a release film such as polyethylene terephthalate (PET), and then cured by ultraviolet (UV) or the like to obtain an OCA sheet. The curable adhesive layer composition may be an optical pressure-sensitive adhesive such as an acrylic resin, a silicone resin, or a urethane resin. After laminating this OCA sheet to an object, the release film is peeled off and removed to obtain a layer consisting of the OCA.
The second bonding layer 32 made of OCA has optical transparency, and preferably has heat resistance, moist heat resistance, and weather resistance up to at least about 120°C.
The thickness of the second bonding layer 32 may be appropriately selected depending on the material thereof, etc. Specifically, the thickness of the second bonding layer 32 may be 30 μm or more and 500 μm or less, and is preferably 50 μm or more and 200 μm or less.

In an embodiment of the present disclosure, the first bonding layer 31 directly bonds the first glass plate 41 and the liquid crystal cell 10. Furthermore, the second bonding layer 32 directly bonds the second glass plate 42 and the liquid crystal cell 10. However, this is not limiting, and a film such as an ultraviolet (UV) blocking film may be interposed in at least one location between the first glass plate 41 and the liquid crystal cell 10 and between the second glass plate 42 and the liquid crystal cell 10.

The first bonding layer 31 and the second bonding layer 32 are bonded bodies containing a non-pressure-bonding adhesive component. Here, a "bonded body containing a non-pressure-bonding adhesive component" refers to a bonded body that does not require pressure to properly bond to adjacent objects, and that can adequately bond to adjacent objects under normal pressure.

The liquid crystal cell 10 (light control film, liquid crystal film) is a film that can control the amount of transmitted light by changing the applied voltage. The liquid crystal cell 10 is disposed so as to be sandwiched between a first glass plate 41 and a second glass plate 42.
In the embodiment of the present disclosure, an example will be described in which the liquid crystal cell 10 has a square shape in plan view.
The liquid crystal cell 10 has a guest-host liquid crystal layer using a dichroic dye, and is a component that changes the amount of light transmitted by an electric field applied to the liquid crystal. The liquid crystal cell 10 includes a first film-like laminate 12, a second film-like laminate 13, and a liquid crystal layer 14 disposed between the first laminate 12 and the second laminate 13.

As shown in Figure 2, the first laminate 12 includes a first substrate 21A, a first transparent electrode 22A, and a first alignment layer 23A, and is stacked in the order of the first substrate 21A, the first transparent electrode 22A, and the first alignment layer 23A from the first bonding layer 31 side.
In addition, the second laminate 13 includes a second substrate 21B, a second transparent electrode 22B, and a second alignment layer 23B, and is stacked in the order of the second substrate 21B, the second transparent electrode 22B, and the second alignment layer 23B from the second bonding layer 32 side.

Furthermore, a plurality of bead spacers 24 are disposed between the first laminate 12 and the second laminate 13. The liquid crystal layer 14 is formed by filling a liquid crystal material between the plurality of bead spacers 24 between the first laminate 12 and the second laminate 13.
The plurality of bead spacers 24 may be arranged irregularly or regularly.

By driving the first transparent electrode 22A and the second transparent electrode 22B provided on the first laminate 12 and the second laminate 13, the liquid crystal cell 10 changes the orientation of the liquid crystal material made of a guest-host liquid crystal composition in the liquid crystal layer 14, thereby changing the amount of transmitted light.

The first substrate 21A and the second substrate 21B may be made of a transparent resin and may be a flexible film, and it is desirable to use a transparent resin film having small optical anisotropy and a transmittance of 80% or more in the visible wavelength range (380 nm to 800 nm).
Examples of materials for such transparent resin films include acetylcellulose resins such as triacetylcellulose (TAC), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin resins such as polyethylene (PE), polypropylene (PP), polystyrene, polymethylpentene, and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, acrylic resins, polyurethane resins, polysulfone (PSF), polyethersulfone (PES), polycarbonate (PC), polyether, polyetherketone (PEK), (meth)acrylonitrile, cycloolefin polymer (COP), and cycloolefin copolymer. Resins such as polycarbonate, cycloolefin polymer, and polyethylene terephthalate are particularly preferred as materials for transparent resin films.

The thickness of the transparent resin films used as the first substrate 21A and the second substrate 21B may be selected appropriately within a range in which the transparent resin films are flexible, depending on the material of the transparent resin films. The thickness of the first substrate 21A and the second substrate 21B may be 50 μm or more and 200 μm or less.
In the embodiment of the present disclosure, a polyethylene terephthalate film having a thickness of 125 μm is used as an example of the first substrate 21A and the second substrate 21B.

The first transparent electrode 22A and the second transparent electrode 22B are composed of a transparent conductive film laminated on the first substrate 21A and the second substrate 21B (transparent resin film), respectively. The transparent conductive film can be made of any of the various transparent electrode materials used in this type of transparent resin film, including oxide-based transparent metal thin films with a total light transmittance of 50% or more. Examples include tin oxide-based, indium oxide-based, and zinc oxide-based materials.

Examples of tin oxide (SnO ₂ )-based materials include NESA (tin oxide SnO ₂ ), ATO (antimony tin oxide), and FTO (fluorine-doped tin oxide). Examples of indium oxide (In ₂ O ₃ )-based materials include indium oxide, ITO (indium tin oxide), and IZO (indium zinc oxide). Examples of zinc oxide (ZnO)-based materials include zinc oxide, AZO (aluminum-doped zinc oxide), and GZO (gallium-doped zinc oxide). In the embodiment of the present disclosure, the transparent conductive films constituting the first transparent electrode 22A and the second transparent electrode 22B are formed of ITO.

The bead spacers 24 are members that define the thickness (cell gap) of the liquid crystal layer 14 .
In the embodiment of the present disclosure, spherical bead spacers are used as the bead spacers 24. The diameter of the bead spacers 24 may be in the range of 1 μm or more and 20 μm or less, preferably 3 μm or more and 15 μm or less.
The bead spacers 24 can be made of a wide range of materials, including inorganic materials such as silica, organic materials, and core-shell structures that combine these materials.
The bead spacers 24 may be configured in a spherical shape, or may be configured in a rod shape such as a cylindrical shape, an elliptical cylindrical shape, a polygonal prism shape, etc. The bead spacers 24 are manufactured from a transparent material, but may be made of a colored material to adjust the color as needed.

In the embodiment of the present disclosure, the bead spacers 24 are provided on the second laminate 13, but this is not limited to this and they may be provided on both the first laminate 12 and the second laminate 13, or only on the first laminate 12. Furthermore, the bead spacers 24 do not necessarily have to be provided. Furthermore, columnar spacers may be used instead of or in addition to the bead spacers 24.

The first alignment layer 23A and the second alignment layer 23B are members for aligning the liquid crystal molecules contained in the liquid crystal layer 14 in a desired direction.
The first alignment layer 23A and the second alignment layer 23B are formed by a photo-alignment layer. As a photo-alignment material applicable to the photo-alignment layer, a wide variety of materials to which a photo-alignment technique can be applied can be used, and examples thereof include a photodecomposition type, a photodimerization type, and a photoisomerization type.
In an embodiment of the present disclosure, a photodimerization type material is used. Examples of the photodimerization type material include polymers having cinnamate, coumarin, benzylidenephthalimidine, benzylideneacetophenone, diphenylacetylene, stilbazole, uracil, quinolinone, maleimide, or cinnamylideneacetic acid derivatives. Among these, polymers having one or both of cinnamate and coumarin are preferably used because of their excellent alignment control power.

Instead of the photo-alignment layer, a rubbed alignment layer may be used. The rubbed alignment layer may not be subjected to a rubbing treatment, or may be prepared by subjecting the layer to a rubbing treatment followed by a shaping treatment to form fine line-shaped irregularities.
Furthermore, in the embodiment of the present disclosure, the liquid crystal cell 10 has a first alignment layer 23A and a second alignment layer 23B, but this is not limited thereto, and the liquid crystal cell 10 may have a configuration that does not have the first alignment layer 23A and the second alignment layer 23B.

A wide variety of guest-host liquid crystal compositions and dichroic dye compositions can be applied to the liquid crystal layer 14. The guest-host liquid crystal composition may contain a chiral agent so that the liquid crystal material is aligned in a helical shape in the thickness direction of the liquid crystal layer 14 when aligned horizontally.
Furthermore, a sealant 25 having a ring or frame shape in plan view is disposed between the first laminate 12 and the second laminate 13 so as to surround the liquid crystal layer 14. The sealant 25 holds the first laminate 12 and the second laminate 13 together and prevents leakage of the liquid crystal material. The sealant 25 may be a thermosetting resin such as an epoxy resin or an acrylic resin, or an ultraviolet curable resin.

For the liquid crystal layer 14, a nematic liquid crystal compound, a smectic liquid crystal compound, or a cholesteric liquid crystal compound can be used as a liquid crystal compound having no polymerizable functional group.
Examples of nematic liquid crystal compounds include biphenyl-based compounds, terphenyl-based compounds, phenylcyclohexyl-based compounds, biphenylcyclohexyl-based compounds, phenylbicyclohexyl-based compounds, trifluoro-based compounds, phenyl benzoate-based compounds, phenyl cyclohexylbenzoate-based compounds, phenyl phenylbenzoate-based compounds, phenyl bicyclohexylcarboxylate-based compounds, azomethine-based compounds, azo-based compounds, azooxy-based compounds, stilbene-based compounds, tolan-based compounds, ester-based compounds, bicyclohexyl-based compounds, phenylpyrimidine-based compounds, biphenylpyrimidine-based compounds, pyrimidine-based compounds, and biphenylethyne-based compounds.

Examples of smectic liquid crystal compounds include ferroelectric polymer liquid crystal compounds such as polyacrylates, polymethacrylates, polychloroacrylates, polyoxiranes, polysiloxanes, and polyesters.
Examples of the cholesteric liquid crystal compound include cholesteryl linoleate, cholesteryl oleate, cellulose, cellulose derivatives, and polypeptides.

Dichroic dyes used in the guest-host system are those that are soluble in liquid crystal and have high dichroic properties, such as azo, anthraquinone, quinophthalone, perylene, indigo, thioindigo, merocyanine, styryl, azomethine, and tetrazine dichroic dyes.

The liquid crystal cell 10 is configured as a normally dark cell, with the first alignment layer 23A and the second alignment layer 23B configured as horizontal alignment layers with a pretilt-related alignment force set in a certain direction so that the guest-host liquid crystal composition is aligned in a light-shielded state when no electric field is applied. The liquid crystal cell 10 may also be configured as a normally clear cell, which is aligned in a light-shielded state when an electric field is applied.
Normally dark is a structure in which the transmittance is at its minimum when no voltage is applied to the liquid crystal, resulting in a light-blocking state, whereas normally clear is a structure in which the transmittance is at its maximum when no voltage is applied to the liquid crystal, resulting in a light-transmitting state.

Furthermore, since it is desirable that the scenery and the like seen through the liquid crystal cell 10 in the light-transmitting state be clearly visible, it is desirable that the haze value in the light-transmitting state be low. Specifically, the haze value of the liquid crystal cell 10 in the light-transmitting state is desirably 30% or less, and more desirably 15% or less. To achieve such a low haze value, it is desirable that the liquid crystal mixture does not contain a polymerizable compound.

In the embodiment of the present disclosure, the liquid crystal cell 10 is shown as having a guest-host liquid crystal layer 14, but this is not limited to this. The liquid crystal cell 10 may also be configured to have a liquid crystal layer 14 of a TN (Twisted Nematic) type, a VA (Vertical Alignment) type, an IPS (In-Plane-Switching) type, or other type that does not use a dichroic dye composition. When such a liquid crystal layer 14 is provided, it can function as a light control film by further providing a linear polarization layer on each of the surfaces of the first substrate 21A and the second substrate 21B.

As shown in FIG. 1, the liquid crystal device 1 is provided with a flexible printed wiring board 18 for electrically connecting the first transparent electrode 22A and the second transparent electrode 22B to the outside.
The flexible printed wiring board 18 can be connected by being sandwiched between the first transparent electrode 22A and the second transparent electrode 22B, for example, in a region where the first transparent electrode 22A and the second transparent electrode 22B do not sandwich the liquid crystal layer 14. Note that the flexible printed wiring board 18 may be in a form where it is not sandwiched between the first transparent electrode 22A and the second transparent electrode 22B, for example.

(Method for manufacturing light control device)
Next, a method for manufacturing the liquid crystal device 1 according to the embodiment of the present disclosure will be described.
4A to 4C are cross-sectional views illustrating a method for manufacturing the liquid crystal device 1 according to the embodiment of the present disclosure.
First, as shown in FIG. 4( a ), a second glass plate 42 is prepared.
4(b), a second bonding layer 32 made of OCA is bonded to the second glass plate 42. In this case, for example, an OCA sheet having the second bonding layer 32 and a release film 35 is bonded to the second glass plate 42, and then the release film 35 is peeled off and removed, thereby bonding the second bonding layer 32 to the second glass plate 42. The second bonding layer 32 may be bonded to the entire area of one side of the second glass plate 42, or may be bonded to a partial area.

4(c), a liquid crystal cell 10 that has been separately prepared is bonded to the second bonding layer 32, and the liquid crystal cell 10 is bonded to the second glass plate 42 by the second bonding layer 32. Note that various known methods can be used to manufacture the liquid crystal cell 10.
The second bonding layer 32 made of OCA is a bonding body containing a pressure-insensitive adhesive component as described above. Therefore, the liquid crystal cell 10 and the second glass plate 42 are bonded together without applying pressure (i.e., under environmental pressure (usually atmospheric pressure)). Furthermore, the second bonding layer 32 is bonded to the liquid crystal cell 10 and the second glass plate 42 at room temperature (e.g., 10°C or higher and 30°C or lower).

4( d ), an uncured liquid first bonding material 310 is applied to the liquid crystal cell 10 and the second bonding layer 32 exposed around the liquid crystal cell 10. The first bonding material 310 becomes the first bonding layer 31 after curing and is an OCR material containing OCR. This OCR material is a liquid curable adhesive layer composition containing a polymerizable compound, and may be a liquid curable adhesive layer composition obtained by mixing a base resin such as an acrylic resin, a silicone resin, or a urethane resin with an additive.
The first bonding material 310 is applied to the entire area or a part of one surface of the liquid crystal cell 10 and the second bonding layer 32 exposed around the liquid crystal cell 10 using an application nozzle 50 such as a dispenser or a slit coater.

Next, as shown in FIG. 4(e), a first glass plate 41 is prepared and laminated on a first bonding material 310. The first glass plate 41 is then bonded to the liquid crystal cell 10 and the second bonding layer 32 exposed around the liquid crystal cell 10 using the first bonding material 310. The first glass plate 41 is laminated on the first bonding material 310 so that the convex surface 41a (see FIG. 3) of its curved shape faces the liquid crystal cell 10. In addition, in a plan view, the first glass plate 41 is laminated so that point C, which is its geometric center, coincides with the center of the liquid crystal cell 10. The thickness of the first bonding layer 31 changes in accordance with the curved shape of the first glass plate 41, so that the thickness at the center of the liquid crystal cell 10 is thinner than the thickness at the outer periphery of the liquid crystal cell 10.

The first bonding material 310 is an OCR bonding body containing a pressure-insensitive adhesive component. Therefore, the first glass plate 41 is bonded to the liquid crystal cell 10 by the first bonding material 310 without applying pressure (i.e., under environmental pressure (usually atmospheric pressure)). Furthermore, the first glass plate 41 is bonded to the liquid crystal cell 10 at room temperature (e.g., 10°C or higher and 30°C or lower).
In addition, the first bonding material 310 is in contact with the second bonding layer 32 around the periphery of the liquid crystal cell 10, and the first glass plate 41 and the second glass plate 42 are bonded together via the first bonding material 310 and the second bonding layer 32.

4( f), ultraviolet (UV) rays are irradiated onto the stacked second glass plate 42, second bonding layer 32, liquid crystal cell 10, first bonding material 310, and first glass plate 41, thereby hardening the first bonding material 310. As the first bonding material 310 hardens, a first bonding layer 31 made of OCR is formed.
In this way, the liquid crystal device 1 is obtained in which the first glass plate 41, the first bonding layer 31, the liquid crystal cell 10, the second bonding layer 32, and the second glass plate 42 are laminated together.

(Regarding the thickness of the first bonding layer 31)
Here, the reason why the curved shape of the first glass plate 41 causes the first bonding layer 31 to have a different thickness in the region covering the liquid crystal cell 10 will be described.
5 is a diagram illustrating the thickness of the first bonding layer 31 according to an embodiment of the present disclosure. Fig. 5 shows a cross section of the liquid crystal device 1 taken along a plane that passes through the geometric center of the liquid crystal cell 10 and is parallel to one side of the liquid crystal device 1 (first glass plate 41, second glass plate 42) in a plan view.
In the liquid crystal device 1 according to the embodiment of the present disclosure, the first glass plate 41 has a curved shape in which its surface is a three-dimensional curved surface, and is curved toward the first bonding layer 31 so that point C, which is the geometric center, is most convex in plan view. This point C coincides with the geometric center of the liquid crystal cell 10. Therefore, the thickness of the first bonding layer 31 follows the curved shape of the first glass plate 41, is smallest at position P1, which corresponds to the geometric center of the liquid crystal cell 10 in plan view, and increases toward the outer periphery.

In the cross section shown in Figure 5, the thickness of the first bonding layer 31 at position P1 corresponding to the center of the liquid crystal cell 10 is defined as T1, and the thickness of the first bonding layer 31 at position P2 corresponding to the outer circumferential edge of the liquid crystal cell 10 is defined as T2. The thicknesses T1 and T2 are such that T1<T2. The difference in thickness of the first bonding layer 31 is defined as T (where T=T2-T1). Furthermore, in the cross section passing through the center of the liquid crystal cell 10 and parallel to one side of the liquid crystal cell 10 as shown in Figure 5, the distance from position P1 to position P2 is defined as W.
In this case, it is preferable that the ratio T/W of the thickness difference T of the first bonding layer 31 to the distance W satisfies the following (Equation 1), from the viewpoint of reducing liquid crystal unevenness caused by liquid crystal accumulation that occurs when the liquid crystal device 1 is exposed to a high-temperature environment.
T/W>1.0×10 ^-3 ...(Formula 1)

In the embodiment of the present disclosure, an example is shown in which the first glass plate 41 has a three-dimensional curved shape, and the liquid crystal device 1, the first glass plate 41, and the second glass plate 42 have a square shape in a plan view. However, this is not limited to this. In cases in which the first glass plate 41 has a three-dimensional curved shape and the liquid crystal device 1, the first glass plate 41, and the second glass plate 42 have a rectangular shape in a plan view, it is preferable that, in a cross section parallel to the short or long side of the rectangle and passing through the geometric center of the liquid crystal cell 10, the difference in thickness of the first bonding layer 31 at position P1 corresponding to the center of the liquid crystal cell 10 and position P2 corresponding to the outer peripheral edge of the liquid crystal cell 10 be defined as T, and the distance from position P1 to position P2 be defined as W.

FIG. 6 is a plan view of a liquid crystal device 1X of a comparative example exposed to a high-temperature environment.
The liquid crystal device 1X of the comparative example has the same form as the liquid crystal device 1 of the embodiment of the present disclosure, except that the first glass plate 41 is not curved but flat, and the first bonding layer 31 does not have a layer thickness difference.
When the liquid crystal device 1X is exposed to a high-temperature environment, the liquid crystal material and the like in the liquid crystal layer 14 expand. This expansion of the liquid crystal material pushes the first bonding layer 31 and the second bonding layer 32, which are in contact with the liquid crystal cell 10, outward from the liquid crystal device 1X. At this time, if the force with which the first bonding layer 31 and the second bonding layer 32 push back the liquid crystal cell 10 is weak, the liquid crystal material expands freely, locally widening the thickness (cell gap) of the liquid crystal layer 14, causing the liquid crystal material to be unevenly distributed in the widened portion, resulting in irregularly shaped liquid crystal pools D1 and causing liquid crystal unevenness.

In a high-temperature environment, if the first bonding layer 31 and the second bonding layer 32 have a sufficient force to push back the liquid crystal cell 10 due to thermal expansion, the thickness (cell gap) of the liquid crystal layer 14 can be maintained. This makes it possible to suppress liquid crystal accumulation D1 within the effective area of the liquid crystal device 1, and to suppress the occurrence of liquid crystal unevenness that appears in island shapes within the effective area of the liquid crystal device 1.
In the embodiment of the present disclosure, the first bonding layer 31 is formed using OCR, the first glass plate 41 has a curved shape that is convex toward the liquid crystal cell 10 side, and the layer thickness T2 of the first bonding layer 31 at the outer peripheral edge of the liquid crystal cell 10 is thicker than the layer thickness T1 of the first bonding layer 31 at the center of the liquid crystal cell 10, thereby satisfying the above-mentioned (Equation 1).
Therefore, in the liquid crystal device 1 according to the embodiment of the present disclosure, the first bonding layer 31 presses the first glass plate 41 outward at the outer peripheral edge of the liquid crystal cell 10 and its periphery, and the curved shape of the first glass plate 41 causes the central portion of the liquid crystal cell 10 to be pressed by the first glass plate 41. This causes the liquid crystal accumulation within the effective area of the liquid crystal cell 10 to be dispersed towards the outer periphery of the liquid crystal cell 10, thereby suppressing liquid crystal unevenness.

(Regarding the ratio T/W)
Liquid crystal devices of measurement examples 1 to 5, which have different values of the ratio T/W, were prepared and evaluated for the occurrence of liquid crystal unevenness when placed in a high-temperature environment. The liquid crystal devices of measurement examples 1 to 5 have different curved shapes of the first glass plate 41, which results in different values of the ratio T/W1, but the other configurations are the same.
In each measurement example, the thickness (cell gap) of the liquid crystal layer 14 was 12 μm, the thickness of the liquid crystal cell 10 was 260 μm, the planar size of the liquid crystal device 1 was 300 mm x 300 mm, and the planar size of the liquid crystal cell 10 was 280 mm x 280 mm.
Furthermore, the liquid crystal device of each measurement example was left standing in a high temperature environment (85° C.) for 60 minutes, and then the unevenness of the liquid crystal was visually confirmed.

As shown in Table 1 above, in Measurement Examples 4 and 5, in which the ratio T/W of the thickness of the first bonding layer 31 caused by the curved shape of the first glass plate 41 satisfied T/W>1.0× ^10-3 , liquid crystal accumulation was reduced and no liquid crystal unevenness was observed.
In contrast, liquid crystal unevenness occurred in Measurement Example 2, in which the first glass plate 41 was flat and not curved, and in Measurement Example 1, in which the first glass plate 41 was curved but the ratio T/W did not satisfy T/W > 1.0 × 10 ⁻³ . In Measurement Example 3, the ratio T/W was T/W > 1.0 × 10 ⁻³ , and although liquid crystal unevenness occurred, it was significantly reduced compared to Measurement Examples 1 and 2.
Therefore, it is preferable that the first glass plate 41 has a curved shape that is convex toward the liquid crystal cell 10 side and that the thickness ratio T/W of the first bonding layer 31 satisfies T/W>1.0× ^10-3 , from the viewpoint of suppressing accumulation of liquid crystal in a high-temperature environment and reducing liquid crystal unevenness.

As described above, according to the embodiment of the present disclosure, the first glass plate 41 has a curved shape that is convex toward the liquid crystal cell 10, and the thickness of the first bonding layer 31 made of OCR satisfies the ratio T/W>1.0×10 ⁻³ , so that the occurrence of liquid crystal pooling that occurs in high-temperature environments can be suppressed, and liquid crystal unevenness can be suppressed. This makes it possible to improve the quality and appearance of the liquid crystal device 1.

Conventional bonding layers made of PVB tend to soften in high-temperature environments, which can lead to the problem of liquid crystal accumulation and noticeable liquid crystal unevenness. However, according to an embodiment of the present disclosure, the first bonding layer 31 is made of highly heat-resistant OCR, and the second bonding layer 32 is made of highly heat-resistant OCA. As a result, even if the liquid crystal device 1 is placed in a high-temperature environment, such as the inside of a vehicle in midsummer, the highly heat-resistant OCA and OCR will not soften, preventing liquid crystal accumulation and suppressing liquid crystal unevenness.

(Other embodiments)
In the above-described embodiment, an example was given in which only the first glass plate 41 has a curved shape and the second glass plate 42 is flat, but this is not limited to this, and the second glass plate 42 may also have a curved shape.
Fig. 7 is a diagram showing another embodiment of the liquid crystal device 1. Fig. 7 shows a cross section passing through the center of the liquid crystal device 1 in a plan view and parallel to a side.
7A , the liquid crystal device 1 may have a configuration in which the first glass plate 41 and the second glass plate 42 have curved shapes that are convex in the same direction in the thickness direction of the liquid crystal device 1. In FIG. 7A , in the thickness direction of the liquid crystal device 1, the first glass plate 41 is convex toward the liquid crystal cell 10, and the second glass plate 42 is convex toward the opposite side from the liquid crystal cell 10 (to the outside of the liquid crystal device 1). In this configuration, there is a difference in the magnitude of curvature of the first glass plate 41 and the second glass plate 42, and the thickness of the first bonding layer 31 at the center of the liquid crystal cell 10 in a plan view of the liquid crystal device 1 is smaller than the thickness of the first bonding layer 31 at the outer circumferential edge of the liquid crystal cell 10 along the curvature direction.

Also, as shown in FIG. 7(b), the liquid crystal device 1 may have a configuration in which the second glass plate 42 has a curved shape that is convex in the thickness direction opposite to the first glass plate 41 (toward the inside of the liquid crystal device). In FIG. 7(b), in the thickness direction of the liquid crystal device 1, the first glass plate 41 is convex toward the liquid crystal cell 10, and the second glass plate 42 is also convex toward the liquid crystal cell 10.

The liquid crystal device 1 may have an overall shape that is curved and convex on one side. This curved shape may be a three-dimensional curved surface or a two-dimensional curved surface.
Furthermore, when the liquid crystal device 1 has a curved shape that is convex on one side, the first glass plate 41 may be arranged in the thickness direction of the liquid crystal device 1 so that the surface 41a is convex on the opposite side to the liquid crystal cell 10 side (i.e., the outside of the liquid crystal device 1), and the second glass plate 42 may be arranged so that it is convex on the liquid crystal cell 10 side (i.e., the inside of the liquid crystal device 1).
Even in the case of adopting any of the above-described forms, it is preferable that the ratio T/W of the difference (amount of change) T between the thickness at the center of the liquid crystal cell 10 and the thickness at the outer peripheral edge of the first bonding layer 31, to the distance W from the center of the liquid crystal cell 10 to its outer peripheral edge, satisfies T/W>1.0× ¹⁰⁻³ , from the viewpoint of reducing liquid crystal unevenness caused by accumulation of liquid crystal in a high-temperature environment.

Alternatively, the liquid crystal device 1 and the second glass plate 42 may be flat, and the first glass plate 41 may be two-dimensionally curved along a pair of opposing sides so as to be convex toward the liquid crystal cell 10.
In this case, in a cross section passing through the center of the liquid crystal cell 10 and parallel to the curved side, it is preferable that the ratio T/W of the difference in thickness T between the center and the outer peripheral edge of the liquid crystal cell 10 and the distance W between a point P1 corresponding to the center of the liquid crystal cell 10 and a position P2 corresponding to the outer peripheral edge thereof satisfies T/W>1.0× ^10-3 .
Even in this configuration, the effect of suppressing liquid crystal unevenness can be sufficiently obtained. Note that the effect of suppressing liquid crystal unevenness is greater when the first glass plate 41 is curved three-dimensionally than when it is curved two-dimensionally.

(Modified form)
The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible, and these are also within the scope of the embodiments of the present disclosure.

(1) If the thickness of the first bonding layer 31 satisfies the ratio T/W>1.0×10 ⁻³ , the liquid crystal device 1 may have a configuration in which the first glass plate 41 is bonded to the liquid crystal cell 10 by a second bonding layer made of OCA, and the flat second glass plate 42 is bonded to the first bonding layer 31 made of OCR.

(2) The liquid crystal cell 10 and liquid crystal device 1 are not limited to those that adjust light transmittance, but may also be liquid crystal cells 10 and liquid crystal devices 1 that display information.

Note that the embodiments and variations of the present disclosure can be used in appropriate combinations, but detailed explanations will be omitted. Furthermore, the embodiments of the present disclosure are not limited to the embodiments described above.

REFERENCE SIGNS LIST 1 Liquid crystal device 10 Liquid crystal cell 31 First bonding layer 32 Second bonding layer 12 First laminate 13 Second laminate 14 Liquid crystal layer 18 Flexible printed wiring board 21A First substrate 21B Second substrate 22A First transparent electrode 22B Second transparent electrode 23A First alignment layer 23B Second alignment layer 24 Bead spacer 25 Sealant 31 First bonding layer 310 First bonding material 32 Second bonding layer 35 Release film 41 First glass plate 42 Second glass plate 50 Application nozzle

Claims (3)

a first transparent substrate;
A second transparent substrate;
a liquid crystal cell disposed between the first transparent substrate and the second transparent substrate;
a first bonding layer disposed between the first transparent substrate and the liquid crystal cell;
a second bonding layer disposed between the second transparent substrate and the liquid crystal cell;
A liquid crystal device comprising:
the second transparent substrate is flat,
the first transparent substrate has a curved shape in which its plate surface forms a three-dimensional curved surface, and is curved so that a point that is a geometric center in a plan view is most convex toward the liquid crystal cell side;
The three-dimensional curved surface is a shape that is partially or entirely curved around a plurality of axes that are angled relative to each other,
a thickness of the first bonding layer at the center of the liquid crystal cell is smaller than a thickness of the first bonding layer at an outer peripheral edge of the liquid crystal cell in a cross section that passes through the center of the liquid crystal cell in a plan view of the liquid crystal device and is parallel to one direction parallel to a surface of the liquid crystal device. 2. The liquid crystal device according to claim 1,
the first bonding layer is made of OCR,
a ratio T/W of a difference T between the thickness of the first bonding layer at the center of the liquid crystal cell and the thickness of the first bonding layer at the outer peripheral edge of the liquid crystal cell to a distance W between the center of the liquid crystal cell and the outer peripheral edge of the liquid crystal cell,
T/W>1.0× ^10-3
LCD device that meets your needs. 3. The liquid crystal device according to claim 1,
The liquid crystal device, wherein the second bonding layer is made of an optically active layer (OCA).