JP7038477B2 - Image display device and its manufacturing method - Google Patents

Description

In the present invention, an image display member such as a liquid crystal display panel and a light transmissive cover member such as a curved transparent protective sheet arranged on the surface side thereof are laminated via a light transmissive photocurable resin layer. The present image display device and its manufacturing method.

In the image display device used for in-vehicle information terminals such as car navigation systems, a photocurable resin composition is applied to a flat light-transmitting cover member and temporarily cured by irradiation with ultraviolet rays to form a temporarily cured resin layer. After that, a flat image display member such as a liquid crystal display panel or an organic EL panel is laminated on the temporarily cured resin layer, and then the temporarily cured resin layer is subjected to ultraviolet irradiation again to be main-cured to obtain a photocurable resin layer. (Patent Document 1).

By the way, in order to improve the design and touch feeling of an image display device for an in-vehicle information terminal, it is required to use a light transmissive cover member having a shape curved in one direction. Therefore, it is attempted to manufacture such an image display device according to the manufacturing method described in Patent Document 1. For example, the photocurable resin composition 101 is applied to the concave surface side surface 100a of the curved light transmissive cover member 100 (FIG. 4A), and the temporary curing resin layer 102 is formed by irradiating with ultraviolet rays (FIG. 4B). Attempts have been made to manufacture by laminating a flat image display member 103 on the temporarily cured resin layer 102 (FIG. 4C), but in many cases, the corner 103a of the image display member 103 is the light transmissive cover member 100. It is laminated so as to make line contact with the concave surface 100a.

Japanese Unexamined Patent Publication No. 2014-119520

Generally, when a photocurable resin composition is photocured by irradiation with ultraviolet rays, curing shrinkage occurs, but in the case of the manufacturing method of Patent Document 1 in which a flat image display member is laminated on a flat light transmissive cover member, a surface is formed. Since the coating thickness of the photocurable resin composition in the direction is as thin and uniform as about 150 μm, voids are unlikely to occur even if the photocurable resin layer is cured and shrunk, and the residual stress of the photocurable resin layer with respect to image quality is reduced. The impact was negligible.

On the other hand, when the photocurable resin composition is applied to the concave surface of the light transmissive cover member having a curved shape in one direction, the coating thickness of the photocurable resin composition near the non-curved side is about 0 to 500 μm. However, the coating thickness of the photocurable resin composition at the center of the concave surface is much thicker than the coating thickness near the non-curved side, and in some cases, it becomes as thick as several mm. Therefore, the curing shrinkage of the photocurable resin composition becomes remarkably large in the central portion of the concave portion surface, and as a result, a concave portion is formed in the central portion, and a gap is generated on the display surface of the assembled image display device. Further, even if no voids are formed, there is a concern that color unevenness may occur in the display due to the residual stress of the photocurable resin layer.

An object of the present invention is to solve the above-mentioned problems of the prior art, in which an image display member and a curved light-transmitting cover member arranged on the surface side thereof are photocurable of a photocurable resin composition. When manufacturing an image display device by laminating via a resin layer, voids do not occur on the display surface of the assembled image display device, and even if voids do not occur, the residual stress of the photocurable resin layer causes them. The purpose is to prevent color unevenness in the display.

In an image display device in which an image display member and a curved light transmissive cover member are laminated via a photocurable resin layer, the present inventor determines the width of the transmissive cover member on the concave surface side. By making the width larger than the width of the image and setting the maximum thickness of the photocurable resin layer on which they are laminated so that the image display member does not come into contact with the light transmissive cover member, a gap is generated on the display surface of the image display device. It has been found that it can be prevented from occurring, and that the residual stress of the photocurable resin layer can be reduced to prevent color unevenness in the display.

Further, the present inventor, in the case of manufacturing such an image display device, in order to control the maximum thickness of the photocurable resin layer so that the image display member does not come into contact with the light transmissive cover member. (B) For the curved light-transmitting cover member, an image display member having a width narrower than the width of the light-transmitting cover member on the concave surface side when the image display device is viewed in cross section is light-transmitting on the concave surface. The photocurable resin composition is filled up to a reference line connecting two contact points that are supposed to come into contact with the cover member, and is irradiated with ultraviolet rays to form a first temporarily cured resin layer having a base thickness (b). On the other hand, for the image display member, the thickness corresponding to the thickness obtained by subtracting the maximum thickness from the intended maximum thickness of the photocurable resin layer to the reference line of the temporarily cured resin layer on the light transmissive cover member side, is used. The curable resin composition is applied to a flat image display member, irradiated with ultraviolet rays to form a second temporarily cured resin layer, and (c) these temporarily cured resin layers are bonded together, and further irradiated with ultraviolet rays to perform main curing. By doing so, it was found that a photocurable resin layer controlled to a predetermined maximum thickness exceeding the maximum thickness up to the reference line can be formed, and the production method of the present invention has been completed.

That is, the present invention is an image display device in which an image display member and a curved light transmissive cover member are laminated via a photocurable resin layer.
The width of the light transmissive cover member on the concave surface side is larger than the width of the image display member.
Provided is an image display device in which the maximum thickness of the photocurable resin layer is such that the image display member does not come into contact with the light transmissive cover member.

Further, the present invention relates to the above-mentioned method for manufacturing an image display device.
The following steps (A) to (F):
<Process (A)>
It is assumed that an image display member having a width narrower than the width on the concave surface side of the light transmissive cover member comes into contact with the light transmissive cover member on the concave surface of the curved light transmissive cover member when the image display device is viewed in cross section. The step of filling the photocurable resin composition up to the reference line connecting the two contact points to be formed;
<Process (B)>
A step of irradiating the photocurable resin composition filled in the step (A) with ultraviolet rays to temporarily cure the photocurable resin composition to form a first temporarily cured resin layer;
<Process (C)>
A step of applying a photocurable resin composition having a predetermined thickness on one side of an image display member;
<Process (D)>
A step of irradiating the photocurable resin composition applied in the step (C) with ultraviolet rays to temporarily cure the photocurable resin composition to form a second temporarily cured resin layer;
<Process (E)>
A step of laminating a curved light-transmitting cover member and an image display member so that the first temporarily cured resin layer and the second temporarily cured resin layer face each other;
<Process (F)>
The first temporarily cured resin layer and the second temporarily cured resin layer are irradiated with ultraviolet rays to be main-cured to form a first photocurable resin layer and a second photocurable resin layer, respectively, whereby they are laminated and photocured. Step of forming a resin layer;
Provided is a manufacturing method having the above.

In the image display device of the present invention, an image display member and a curved light transmissive cover member are laminated via a photocurable resin layer, and the width of the transmissive cover member on the concave surface side is the image display member. The maximum thickness of the photocurable resin layer larger than the width and laminating them is such that the image display member does not come into contact with the light transmissive cover member. Therefore, it is possible to prevent voids from being generated on the display surface of the image display device, and it is possible to reduce the residual stress of the photocurable resin layer so that color unevenness of the display does not occur.

FIG. 1 is a cross-sectional view of the image display device of the present invention. FIG. 2A is an explanatory diagram of the light transmissive cover member. FIG. 2B is an explanatory diagram of the light transmissive cover member. FIG. 2C is an explanatory diagram of the light transmissive cover member. FIG. 2D is an explanatory diagram of the light transmissive cover member. FIG. 2E is an explanatory diagram of the light transmissive cover member. FIG. 2F is an explanatory diagram of the light transmissive cover member. FIG. 3A is an explanatory diagram of a step (A) of the manufacturing method of the present invention. FIG. 3B is an explanatory diagram of a step (B) of the manufacturing method of the present invention. FIG. 3C is an explanatory diagram of a step (C) of the manufacturing method of the present invention. FIG. 3D is an explanatory diagram of a step (D) of the manufacturing method of the present invention. FIG. 3E is an explanatory diagram of a step (E) of the manufacturing method of the present invention. FIG. 3F is an explanatory diagram of a step (F) of the manufacturing method of the present invention. FIG. 4A is an explanatory diagram of a method of manufacturing a conventional image display device. FIG. 4B is an explanatory diagram of a method of manufacturing a conventional image display device. FIG. 4C is an explanatory diagram of a method of manufacturing a conventional image display device.

Hereinafter, the image display device of the present invention and the manufacturing method thereof will be described in detail with reference to the drawings. First, the image display device will be described.

The image display device 10 of the present invention shown in FIG. 1 has a structure in which an image display member 1 and a curved light transmissive cover member 2 are laminated via a photocurable resin layer 3. The degree of curvature of the light transmissive cover member 2 can be appropriately set according to the purpose of use of the image display device 10. In the image display device 10, the width Y (for example, 50 to 150 mm, more generally 85 to 100 mm) on the concave surface side of the light transmissive cover member is larger than the width X of the image display member 1. (For example, it is 5 to 30 mm, more generally 10 to 25 mm larger), and the maximum thickness hm of the photocurable resin layer 3 (for example, 0.5 to 4.0 mm, more realistically 1.6). ~ 3.5 mm) is the thickness at which the image display member 1 does not come into contact with the light transmissive cover member 2. Specifically, as shown in FIG. 1, when the image display device 10 is viewed in cross section, the image display member 1 is present when the photocurable resin layer 3 is not present from the bottom portion B of the concave surface of the light transmissive cover member 2. The distance h0 (for example, 0.3 to 3.5 mm, more realistically 1.5 to The maximum thickness hm of the photocurable resin layer 3 is thicker than that of 3.4 mm). With such a structure, even if the photocurable resin layer 3 is cured and shrunk, the image display member 1 is not in contact with the light transmissive cover member 2, so that the stress can be relaxed by the photocurable resin layer 3 itself. Moreover, since the deformation / movement of the image display member 1 is not excessively restricted, it is possible to suppress the occurrence of voids on the display surface of the image display device 10 and the occurrence of color unevenness in the display.

Regarding the formation of the photocurable resin layer 3, it is not impossible, but it is very difficult, to apply the photocurable resin composition to the concave surface of the light transmissive cover member 2 at a time with a required thickness without excess or deficiency. be. In particular, the maximum thickness hm of the photocurable resin layer 3 is the distance h1 from the bottom portion B of the concave surface surface of the light transmissive cover member 2 to the straight line L1 connecting the corners P3 and P4 on the concave surface side of the light transmissive cover member 2. If it is larger than (for example, 3.0 to 4.2 mm), the difficulty becomes remarkable. This is because the photocurable resin composition to be applied has fluidity.

Therefore, in the image display device 10 of the present invention, although the configuration depends on the manufacturing method described later, the photocurable resin layer 3 is the first photocurable resin layer 3a on the light transmissive cover member 2 side and the image display member. It is preferable to have a two-layer structure with the second photocurable resin layer 3b on the one side. Here, the maximum thickness h0 of the first photocurable resin layer 3a is two points P1 in which the image display member 1 is assumed to come into contact with the light transmissive cover member 2 from the concave surface bottom portion B of the light transmissive cover member 2. , Corresponds to the distance to the reference line L0 connecting P2. With such a two-layer structure, the second photocurable resin layer 3b having a thickness (for example, 0.03 to 1.5 mm) corresponding to the thickness obtained by subtracting h0 from hm on the flat image display member 1 Is easy to form.

(Image display member 1)
Examples of the image display member 1 constituting the image display device 10 of the present invention include a liquid crystal display panel, an organic EL display panel, a plasma display panel, and a touch panel. Here, the touch panel means an image display / input panel in which a display element such as a liquid crystal display panel and a position input device such as a touch pad are combined.

(Light transmissive cover member 2)
The specific shape of the curved light transmissive cover member 2 is a shape curved in one direction (for example, a shape on the inferior arc side obtained by cutting a cylindrical pipe in a plane parallel to its central axis (hereinafter, horizontal trough). (Referred to as a shape)) (FIG. 2A), a shape curved in the X and Y directions (FIG. 2B), and a shape curved in the 360 ° direction (for example, obtained by cutting a sphere in a plane not including its center point). Shape on the inferior arc side) (Fig. 2C) and the like. A flat portion 2b may be formed in the central portion of these shapes (for example, FIG. 2D).

When the light transmissive cover member 2 has a horizontal trough shape (FIG. 2A), the inner dam material 20 (FIG. 2E) or the inner dam material 20 (FIG. 2E) that defines the coating region of the photocurable resin composition inside the both end portions 2x and 2y. It is preferable to provide the outer dam material 21 (FIG. 2F) that defines the coating region of the photocurable resin composition on the outer sides of both ends 2x and 2y. As the inner dam material 20 and the outer dam material 21, the applied photocurable resin composition can be dammed without being compatible with the coated photocurable resin composition, and can be easily removed after the photocurable resin composition is temporarily cured. It can be formed from any known material. For example, as the inner dam material 20, a known thermoplastic elastomer tape having a slightly adhesive layer or the like is attached to the inside of the end portion of the light transmissive cover member 2 in a bank shape. Examples of the outer dam material 21 include a silicone sheet and a fluororesin sheet.

When the light transmissive cover member 2 has the embodiment shown in FIGS. 2B and 2C, the dam material may be omitted. Further, even in the case of the aspect of FIG. 2A, a surface treatment (for example, photocuring) for preventing the flow of the photocurable resin composition on the surface of the light transmissive cover member 2 corresponding to the inner dam material 20 is performed. Depending on the characteristics of the sex resin composition, roughening treatment, hydrophilization treatment, water repellent treatment, etc.) may be performed.

The material of the light-transmitting cover member 2 may be any material as long as it has light-transmitting property so that the image formed on the image display member can be visually recognized, and a resin such as glass, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, or polycarbonate. Materials are mentioned. These materials can be subjected to single-sided or double-sided hardcourt treatment, antireflection treatment, and the like. Dimensional characteristics such as the curved shape and thickness of the light transmissive cover member 1, and physical properties such as elasticity can be appropriately determined according to the purpose of use.

(Photo-curing resin layer 3)
The photocurable resin layer 3 that joins the image display member 1 and the light transmissive cover member 2 is a layered photocurable product of the photocurable resin composition, and makes the image displayed by the image display member 1 visible. Has light transmission. The properties of the photocurable resin composition constituting the photocurable resin layer 3 are preferably liquid. When a liquid material is used, the recesses of the light-transmitting cover member 2 can be filled with the photocurable resin composition so that the surface of the composition is flat. Here, the liquid means a viscosity of 0.01 to 100 Pa · s (25 ° C.) with a cone plate type viscometer.

Such a photocurable resin composition preferably comprises a base component (component (a)), an acrylate-based monomer component (component (b)), and a photopolymerization initiator (component (c)). be able to. Further, a plasticizer component (component (d)) can be contained. The final curing shrinkage of the photocurable resin composition is preferably 3% or more. It may be 5% or more.

Here, the "final curing shrinkage rate" means the curing shrinkage rate generated between the uncured state and the completely cured state of the photocurable resin composition. Here, "completely cured" means a state of being cured so that the curing rate is at least 90%, as will be described later. Hereinafter, the final curing shrinkage rate is referred to as a total curing shrinkage rate. Further, the curing shrinkage rate generated between the uncured state and the temporarily cured state of the curable resin composition is referred to as a temporary curing shrinkage rate. Further, in the main curing step, the curing shrinkage rate generated between the temporarily cured state and the completely cured state is referred to as the main curing shrinkage rate.

For the total curing shrinkage rate of the photocurable resin composition, the specific densities of the uncured (in other words, before curing) composition and the completely cured solid solid product after complete curing are measured by an electronic specific gravimeter (SD manufactured by Alpha Mirage Co., Ltd.). -120L) can be used for measurement, and the difference in specific gravity between the two can be calculated by the following equation. Further, the temporary curing shrinkage rate of the temporary curing resin of the photocurable resin composition is the specific gravity of the uncured (in other words, before curing) composition and the solid temporary cured product after the temporary curing, which is measured by an electron specific gravity meter (alpha). It can be measured using SD-120L manufactured by Mirage Co., Ltd., and can be calculated by the following formula from the difference in specific gravity between the two. The main curing shrinkage rate can be calculated by subtracting the temporary curing shrinkage rate from the total curing shrinkage rate.

The base component of the component (a) is a film-forming component of the photocurable resin layer, and is a component containing at least one of an elastomer and an acrylate-based oligomer. Both may be used together as a component (a).

As the elastomer, preferably, an acrylic copolymer composed of a copolymer of an acrylic acid ester, polybutene, polyolefin and the like can be mentioned. The weight average molecular weight of this acrylic acid ester copolymer is preferably 5000 to 500,000, and the number of repetitions n of polybutene is preferably 10 to 10,000.

On the other hand, examples of the acrylate-based oligomer preferably include (meth) acrylate-based oligomers having polyisoprene, polyurethane, polybutadiene, or the like in the skeleton. In addition, in this specification, the term "(meth) acrylate" includes acrylate and methacrylate.

Preferred specific examples of the (meth) acrylate oligomer having a polyisoprene skeleton include an esterified product of a maleic anhydride adduct of a polyisoprene polymer and 2-hydroxyethyl methacrylate (UC102 (polystyrene equivalent molecular weight of about 17,000), Kuraray Co., Ltd.). UC203 (polystyrene equivalent molecular weight about 35,000), Kuraray Co., Ltd .; UC-1 (polystyrene equivalent molecular weight about 25,000), Kuraray Co., Ltd.) and the like can be mentioned.

Further, as a preferable specific example of the (meth) acrylate-based oligomer having a polyurethane skeleton, an aliphatic urethane acrylate (EBECRYL230 (molecular weight 5000), Daicel Ornex Co., Ltd .; UA-1, Light Chemical Industry Co., Ltd.) and the like are used. Can be mentioned.

As the (meth) acrylate-based oligomer having a polybutadiene skeleton, known ones can be adopted.

The acrylate-based monomer component of the component (b) is used as a reactive diluent in order to impart sufficient reactivity, coatability, etc. to the photocurable resin composition in the manufacturing process of the image display device. Examples of such acrylate-based monomers include 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, stearyl acrylate, benzyl acrylate, tetrahydrofrifuryl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl methacrylate, isobornyl acrylate, and di. Cyclopentanyl acrylate, lauryl methacrylate and the like can be mentioned.

As the photopolymerization initiator of the component (c), a known photoradical polymerization initiator can be used, and for example, 1-hydroxy-cyclohexylphenyl ketone (Irgacure 184, BASF Japan Co., Ltd.), 2- Hydroxy-1- {4- [4- (2-1 hydroxy-2-methyl-propironyl) benzyl] phenyl} -2-methyl-1-propan-1-one (Irgacure 127, BASF Japan Co., Ltd.), benzophenone, Acetphenone and the like can be mentioned.

If the amount of such a photopolymerization initiator is too small with respect to a total of 100 parts by mass of the acrylate-based oligomer and the monomer (component (b)) in the base component (a), the curing will be insufficient when irradiated with ultraviolet rays, and if it is too large, it will be cleaved. Since the amount of outgas increases and there is a tendency for foaming defects, the amount is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass.

In addition, the photocurable resin composition can contain a chain transfer agent for adjusting the molecular weight. For example, 2-mercaptoethanol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, α-methylstyrene dimer and the like can be mentioned.

The plasticizer component of the component (d) is used to impart cushioning properties to the photocurable resin layer and reduce the curing shrinkage rate of the photocurable resin composition, and is the base of the component (a) when irradiated with ultraviolet rays. It does not react with the acrylate-based monomer component of the component and the component (b). Such a plasticizer component contains a solid tackifier (1) and a liquid oil component (2).

Examples of the solid tackifier (1) include terpene resins such as terpene resin, terpene phenol resin and hydrogenated terpene resin, rosin resins such as natural rosin, polymerized rosin, rosin ester and hydrogenated rosin, and terpene hydrogenated resin. Can be mentioned. In addition, a non-reactive oligomer obtained by preliminarily converting the above-mentioned acrylate-based monomer into a low-molecular polymer can also be used. Specifically, a copolymer of butyl acrylate and 2-hexyl acrylate and acrylic acid, or cyclohexyl acrylate and methacrylic can be used. Examples thereof include acid copolymers.

As the liquid oil component (2), a polyptadiene-based oil, a polyisoprene-based oil, or the like can be contained.

Further, the photocurable resin composition can further contain a general additive such as an adhesion improving agent such as a silane coupling agent and an antioxidant, if necessary.

Since the curing shrinkage of the photocurable resin composition is preferably suppressed to less than 3%, it is basically not essential to contain a plasticizer component, but the photocurable resin layer 3 has a cushioning property. A plasticizer component (component (d)) can be contained within a range that does not impair the effects of the present invention. Therefore, the total content of the base component of the component (a) and the acrylate-based monomer component of the component (b) in the photocurable resin composition is preferably 25 to 85% by mass, but the plasticity of the component (d). The content of the agent component is in the range of 0 to 65% by mass.

The image display device of the present invention can be manufactured by a manufacturing method having the following steps (A) to (F). Hereinafter, each process will be described in detail with reference to the drawings.

<Step (A): Filling step>
First, as shown in FIG. 3A, an image is displayed on the concave surface of the curved light transmissive cover member 2 with a width narrower than the width on the concave surface side of the light transmissive cover member 2 when the image display device is viewed in cross section. The photocurable resin composition 30 is filled with the dispenser D or the like up to the reference line L0 connecting the two contact points P1 and P2 where the member is assumed to come into contact with the light transmissive cover member.

<Step (B): First temporary curing resin layer forming step>
Next, as shown in FIG. 3B, the photocurable resin composition 30 filled in the step (A) is irradiated with ultraviolet UV rays and temporarily cured to form the first temporarily cured resin layer 30a. Here, the purpose of temporary curing is to improve the handleability by keeping the photocurable resin composition 30 in a non-flowing state. As for the level of such temporary curing, the curing rate (gel fraction) of the first temporary curing resin layer 30a is preferably 10% or more and 90% or less, more preferably 40% or more and 90% or less, and particularly 60% or more and 90%. The level is as follows. The curing rate (gel fraction) is the ratio (consumption) of the abundance of (meth) acryloyl groups after ultraviolet irradiation to the abundance of (meth) acryloyl groups in the photocurable resin composition 30 before ultraviolet irradiation. It is a numerical value defined as (quantity ratio), and the larger this numerical value is, the more the curing is progressing.

The curing rate (gel fraction) is the absorption peak height (hx) of 1640 to 1620 cm ^-1 from the baseline in the FT-IR measurement chart of the resin composition layer before UV irradiation, and the resin after UV irradiation. The absorption peak height (hy) of 1640 to 1620 cm ^-1 from the baseline in the FT-IR measurement chart of the composition layer can be calculated by substituting it into the following formula.

Regarding irradiation with ultraviolet rays, the type, output, cumulative amount of light, etc. of the light source are not particularly limited as long as they can be temporarily cured so that the curing rate (gel fraction) is preferably 10 to 80%, and known ultraviolet irradiation is performed. The photoradical polymerization process conditions of (meth) acrylate can be adopted.

Further, regarding the ultraviolet irradiation conditions, the dripping of the first temporarily cured resin layer 30a and the second temporarily cured resin layer 31b during the bonding operation in the laminating step of the step (E) described later within the range of the above-mentioned curing rate. It is preferable to select conditions that do not cause deformation. Expressing the conditions under which such dripping and deformation do not occur in terms of viscosity is 20 Pa · S or more (cone plate leometer, 25 ° C., cone and plate C35 / 2, rotation speed 10 rpm).

The level of curing in the temporary curing is from the first temporary curing resin layer 30a and the second temporary curing resin layer 31b to the first photocuring resin layer 3a and the second photocuring resin layer 3b in the main curing step (F) described later, respectively. It is cured so that the curing shrinkage rate generated between the two is less than 3%. That is, in the case of the photocurable resin compositions 30 and 31 having a total curing shrinkage rate of 5%, the temporary curing shrinkage is performed by at least 2% at the time of temporary curing.

When the inner dam material 20 (see FIG. 2E) and the outer dam material 21 (see FIG. 2F) are provided prior to the filling in the step (A), after the step (B) and before the step (F), It is preferable to remove the inner dam material 20 or the outer dam material 21. This is because the photocurable resin composition has already been temporarily cured and the resin does not flow.

<Step (C): Coating step>
Next, as shown in FIG. 3C, a photocurable resin composition 31 having a predetermined thickness is applied to one side of the image display member 1 using a dispenser or the like. As the photocurable resin composition 31, it is preferable to use the same one as described in the step (A). As shown in FIG. 1, the photocurable resin composition 31 is applied so that the maximum thickness hm of the photocurable resin layer 3 is such that the image display member 1 does not come into contact with the light transmissive cover member 2. ..

<Step (D): Second temporary curing resin layer forming step>
Next, as shown in FIG. 3D, the photocurable resin composition 31 applied in the step (C) is irradiated with ultraviolet UV under the same operations and conditions as in the step (B) to be temporarily cured. 2 The temporarily cured resin layer 31b is formed.

<Process (E): Laminating process>
Subsequently, the curved light transmissive cover member 2 and the image display member 1 are laminated so that the first temporarily cured resin layer 30a and the second temporarily cured resin layer 31b face each other (FIG. 3E). Laminating can be performed by pressurizing at 10 ° C to 80 ° C using a known crimping device, but the first temporarily cured resin layer 30a, the second temporarily cured resin layer 31b, the image display member 1, and light transmission can be performed. In order to prevent air bubbles from entering the respective interfaces with the property cover member 2, it is preferable to perform laminating by a so-called vacuum bonding method.

In addition, between the step (E) and the step (F), a known pressure defoaming treatment (treatment condition example: 0.2 to 0.8 MPa, 25 to 60 ° C., 5 to 20 min) is performed on the laminate. Is preferable.

<Step (F): Main curing step>
Subsequently, as shown in FIG. 3F, the first temporarily cured resin layer 30a and the second temporarily cured resin layer 31b sandwiched between the image display member 1 and the light transmissive cover member 2 are irradiated with ultraviolet UV rays. Then, it is finally cured to form a first photocurable resin layer 3a and a second photocurable resin layer 3b, respectively, to form a photocurable resin layer 3 in which they are laminated. As a result, the image display device shown in FIG. 1 is obtained. In this step, the main curing is to sufficiently cure the first temporarily cured resin layer 30a and the second temporarily cured resin layer 31b, and the image display member 1 and the light transmissive cover member 2 are adhered and laminated. Because. Such a level of main curing is such that the curing rate (gel fraction) of the light-transmitting photo-curing resin layer 3 is preferably more than 90%, more preferably 95% or more and 100% or less. ..

The level of light transmission of the photocurable resin layer 3 may be such that the image formed on the image display member 1 can be visually recognized.

Hereinafter, the present invention will be specifically described with reference to Examples. In the following examples, the total curing shrinkage rate, the temporary curing shrinkage rate, and the main curing shrinkage rate of the photocurable resin composition are the specific gravity of the photocurable resin composition, the temporary curing product, and the completely cured product, respectively. The specific gravity was measured using an electronic specific gravity meter (SD-120L manufactured by Alpha Mirage Co., Ltd.), and the measurement results were applied to the following equations for calculation.

Example 1
(Step (A): Filling step)
First, a transparent resin plate (polyethylene terephthalate plate) having a size of 45 (w) × 80 (l) × 3 (t) mm is prepared, and a known method is used so that the radius of curvature is 300 mm (r) in the width direction. A resin cover (FIG. 2A) was obtained as a curved and curved horizontal trough-shaped light-transmitting cover member.

Separately, 50 parts by mass of an acrylate-based oligomer having a polybutadiene skeleton (TE-2000, Nippon Soda Co., Ltd.), 20 parts by mass of hydroxyethyl methacrylate, and 10 parts by mass of a photopolymerization initiator (Irgacure 184, manufactured by BASF Japan Co., Ltd.). A photocurable resin composition was prepared by uniformly mixing 3 parts by mass, SpeedCure TPO, and 7 parts by mass of DKSH Japan Co., Ltd.). This photocurable resin composition exhibited a total curing shrinkage rate of 5.6% between 0% and 90%.

Next, both ends of the horizontal trough-shaped resin cover were sandwiched between two silicone rubber sheets as an outer dam material (FIG. 2F). The prepared photocurable resin composition is discharged into the recesses of the resin cover using a resin dispenser so that the thickness at the center is 670 μm and the width is 40 mm. Formed.

(Step (B): First temporary curing resin layer forming step)
Next, the photocurable resin composition film prepared in the step (A) was subjected to an ultraviolet irradiation device (LC-8, manufactured by Hamamatsu Photonics Co., Ltd.) so that the integrated light amount was 1200 mJ / cm ² . The photocurable resin composition film was temporarily cured by irradiating it with ultraviolet rays having an intensity of 200 mW / cm ² for 6 seconds to form a first temporarily cured resin layer, and further, the outer dam material was removed. The temporary curing shrinkage rate of the first temporary curing resin layer was 3.8%.

The curing rate of the first temporarily cured resin layer was about 70% when determined using the absorption peak height of 1640 to 1620 cm-1 from the baseline in the FT-IR measurement chart as an index.

(Step (C): Coating step)
Next, the photocurable resin composition used in the step (A) is slit-shaped at the tip on the surface on which the polarizing plate of the flat liquid crystal display element having a size of 40 (W) × 80 (L) mm is laminated. It was applied so that the film thickness would be 100 μm with the dispenser.

(Step (D): Second temporarily cured resin layer forming step)
Next, the photocurable resin composition film prepared in the step (C) was 200 mW so that the integrated light amount was 1200 mJ / cm ² using an ultraviolet irradiation device (LC-8, manufactured by Hamamatsu Photonics). The photocurable resin composition film was temporarily cured by irradiating it with ultraviolet rays having a strength of / cm ² for 6 seconds to form a second temporarily cured resin layer. The temporary curing shrinkage rate of the second temporary curing resin layer was 3.8%, and the curing rate was about 70%.

(Step (E): Laminating step)
Next, the liquid crystal display element on which the second temporarily cured resin layer of the step (D) is formed on the resin cover on which the first temporarily cured resin layer of the step (B) is formed is combined with the first temporarily cured resin layer. 2 The temporarily cured resin layer was placed so as to face each other, and the resin cover was attached from the resin cover side with a vacuum bonding machine (vacuum degree 50 Pa, bonding pressure 0.07 MPa, bonding time 3 seconds, normal temperature).

(Step (F): Main curing step)
Next, the liquid crystal display element is irradiated with ultraviolet rays (200 mW / cm ² ) at 3000 mJ / cm ² from the resin cover side using an ultraviolet irradiation device (ECS-03601EG, Eye Graphics Co., Ltd.). The temporarily cured resin layer was completely cured to form a light-transmitting photo-curing resin layer. The curing rate of this photocurable resin layer was 98%. As a result, a liquid crystal display device in which a curved resin cover as a light transmissive cover member is laminated on the liquid crystal display element via a photocurable resin layer is obtained. The main curing shrinkage rate was 1.8%.

When the presence or absence of voids was visually observed from the glass resin cover side of the obtained liquid crystal display device, no voids were observed at the interface between the glass resin cover and the photocurable resin layer. Moreover, when the display operation was performed, no color unevenness was observed in the display in the center of the glass resin cover. The temporary curing shrinkage rate was 3.8%, and the main curing shrinkage rate was 1.8%.

Comparative Example 1
A liquid crystal display element on which the second temporarily cured resin layer is not formed is placed on the resin cover on which the first temporarily cured resin layer is formed in the step (B) without performing the steps (C) and (D). Then, the same operation as in Example 1 was performed except that the resin cover was attached from the resin cover side with a vacuum bonding machine (vacuum degree 50 Pa, bonding pressure 0.07 MPa, bonding time 3 seconds, normal temperature), and the image display device was displayed. Obtained. When the presence or absence of voids was visually observed from the resin cover side of the obtained liquid crystal display device, bubble-like voids were found in the substantially central portion of the interface between the photocurable resin layer and the liquid crystal display element.

In the image display device of the present invention, an image display member and a curved light transmissive cover member are laminated via a photocurable resin layer, and the width of the transmissive cover member on the concave surface side is the image display member. The maximum thickness of the photocurable resin layer larger than the width and laminating them is such that the image display member does not come into contact with the light transmissive cover member. Therefore, it is possible to prevent voids from being generated on the display surface of the image display device, and it is possible to reduce the residual stress of the photocurable resin layer so that color unevenness of the display does not occur. Therefore, the image display device of the present invention is useful, for example, in the industrial manufacture of an in-vehicle information terminal provided with a touch panel.

1 Image display member 2 Light-transmitting cover member 2b Flat part 2x, 2y Both ends of light-transmitting cover member 3 Photo-curing resin layer 3a First photo-curing resin layer 3b Second photo-curing resin layer 10 Image display device 20 Inner dam Material 21 Outer dam material 30, 31 Photo-curing resin composition 30a First temporary-curing resin layer 31b Second temporary-curing resin layer B Recessed surface side bottom of light-transmitting cover member D Dispenser hm Maximum thickness of photo-curing resin layer h0 Maximum thickness of the first photo-curing resin layer h1 Distance from the bottom B to the straight line L1 L0 Reference line connecting the contact points L1 Straight line connecting the corners on the concave surface side of the light transmissive cover member P1, P2 With the image display member Contact points with the light-transmitting cover member P3, P4 Corner of the light-transmitting cover member on the concave surface side X Width of the image display member Y Width of the light-transmitting cover member on the concave surface side

Claims (9)

An image display device in which an image display member and a curved light transmissive cover member are laminated only via a photocurable resin layer.
The width of the light transmissive cover member on the concave surface side is larger than the width of the image display member.
The maximum thickness of the photocurable resin layer is the thickness at which the image display member does not come into contact with the light transmissive cover member .
The distance from the bottom of the concave surface of the light-transmitting cover member to the reference line connecting the two contact points where the image-transmitting member is assumed to come into contact with the light-transmitting cover member when the image display device is viewed in cross section. , The maximum thickness of the photocurable resin layer is thick,
The photo-curing resin layer has a two-layer structure of a first photo-curing resin layer on the light-transmitting cover member side and a second photo-curing resin layer on the image display member side, and the maximum thickness of the first photo-curing resin layer. The image display device corresponds to the distance from the bottom of the concave surface of the light transmissive cover member to the reference line connecting two points where the image display member is assumed to come into contact with the light transmissive cover member . The image display device according to claim 1 , wherein the image display member is a liquid crystal display panel, an organic EL display panel, a plasma display panel, or a touch panel. The photocurable resin composition is a liquid resin composition containing at least one of an elastomer and an acrylate-based oligomer, an acrylic-based monomer, and a photopolymerization initiator.
The elastomer is at least one selected from the group consisting of acrylic copolymers, polybutenes and polyolefins.
The image display device according to claim 1 or 2 , wherein the acrylate-based oligomer is at least one selected from the group consisting of polyurethane-based (meth) acrylates, polybutadiene-based (meth) acrylates, and polyisoprene-based (meth) acrylates. The image display member and the curved light transmissive cover member are laminated only via the photocurable resin layer, and the width of the light transmissive cover member on the concave surface side is larger than the width of the image display member, and the photocurable resin. In the method for manufacturing an image display device, the maximum thickness of the layer is such that the image display member does not come into contact with the light transmissive cover member .
The following steps (A) to (F):
<Process (A)>
It is assumed that an image display member having a width narrower than the width on the concave surface side of the light transmissive cover member comes into contact with the light transmissive cover member on the concave surface of the curved light transmissive cover member when the image display device is viewed in cross section. The step of filling the photocurable resin composition up to the reference line connecting the two contact points to be formed;
<Process (B)>
A step of irradiating the photocurable resin composition filled in the step (A) with ultraviolet rays to temporarily cure the photocurable resin composition to form a first temporarily cured resin layer;
<Process (C)>
A step of applying a photocurable resin composition having a predetermined thickness on one side of an image display member;
<Process (D)>
A step of irradiating the photocurable resin composition applied in the step (C) with ultraviolet rays to temporarily cure the photocurable resin composition to form a second temporarily cured resin layer;
<Process (E)>
A step of laminating a curved light-transmitting cover member and an image display member so that the first temporarily cured resin layer and the second temporarily cured resin layer face each other directly;
<Process (F)>
The first temporarily cured resin layer and the second temporarily cured resin layer are irradiated with ultraviolet rays to be main-cured to form a first photocurable resin layer and a second photocurable resin layer, respectively, whereby they are laminated and photocured. Step of forming a resin layer;
Manufacturing method having. The curing rates of the first temporarily cured resin layer in the step (B) and the second temporarily cured resin layer in the step (D) are 10% or more and 90% or less, respectively, and the curing rate of the photocurable resin layer in the step (F) is 4. The manufacturing method according to claim 4 , wherein is greater than 90% and 100% or less. The fourth or fifth aspect of the present invention, wherein a dam member capable of filling the photocurable resin composition up to the reference line on the concave surface side of the curved light transmissive cover member is provided on the concave surface prior to the filling in the step (A). Manufacturing method. The manufacturing method according to any one of claims 4 to 6 , wherein a pressure defoaming treatment is performed between the step (E) and the step (F). The manufacturing method according to any one of claims 4 to 7 , wherein the image display member is a liquid crystal display panel, an organic EL display panel, a plasma display panel, or a touch panel. The photocurable resin composition is a liquid resin composition containing at least one of an elastomer and an acrylate-based oligomer, an acrylic-based monomer, and a photopolymerization initiator.
The elastomer is at least one selected from the group consisting of acrylic copolymers, polybutenes and polyolefins.
The production method according to any one of claims 4 to 8 , wherein the acrylate-based oligomer is at least one selected from the group consisting of polyurethane-based (meth) acrylate, polybutadiene-based (meth) acrylate, and polyisoprene-based (meth) acrylate. ..

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