JP2018128668A - Method for manufacturing image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an image display device which prevents a void on a display surface of an assembled image display device and prevents color unevenness of display due to a residual stress of a photocurable resin layer, when the image display device is manufactured by layering an image display member, a curved light transmitting cover member arranged on the surface side through a curable resin layer of the photocurable resin composition.SOLUTION: A method for manufacturing an image display device includes: applying a photocurable resin composition onto a recessed surface of a curved light transmitting cover member; irradiating the applied photocurable resin composition with ultraviolet rays to temporarily cure the photocurable resin composition; forming a temporarily-cured resin layer having a slight recess based on curing and contraction of the photocurable resin composition in a central part of the recess surface; applying an amount corresponding to the slight recess of the temporarily-cured resin layer of the photocurable resin composition onto the temporarily-cured resin layer or an image display member; layering the image display member and the light transmitting cover member through the temporarily-cured resin layer; and irradiating the temporarily-cured resin layer sandwiched between the image display member and the light transmitting cover member with ultraviolet rays and finally curing the temporarily-cured resin layer to form a light transmitting cured resin layer.SELECTED DRAWING: Figure 1A

Description

  The present invention provides an image in which an image display member such as a liquid crystal display panel and a light-transmitting cover member such as a curved transparent protective sheet disposed on the surface side are laminated via a light-transmitting cured resin layer. The present invention relates to a method for manufacturing a display device.

  An image display device used in an in-vehicle information terminal such as a car navigation system forms a temporarily cured resin layer by applying a photocurable resin composition to a flat light-transmitting cover member and temporarily curing by ultraviolet irradiation. 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 subsequently, the temporary cured resin layer is subjected to ultraviolet irradiation again to be fully cured to form a photocurable resin layer. (Patent Document 1).

  By the way, in order to improve the designability and touch feeling of an image display device for in-vehicle information terminals, it is required to use a light-transmitting cover member having a shape curved in one direction. For this reason, it has been attempted to manufacture such an image display device according to the manufacturing method described in Patent Document 1.

JP 2014-119520 A

  Generally, when the photocurable resin composition is photocured by ultraviolet irradiation, curing shrinkage occurs. However, in the case of the manufacturing method of Patent Document 1 in which a flat image display member is laminated on a flat light-transmitting cover member, Since the coating thickness of the photocurable resin composition in the direction is as thin as about 150 μm and uniform, voids hardly occur even when the photocurable resin layer is cured and contracted, and the residual stress of the photocurable resin layer with respect to image quality The effect was negligible.

  On the other hand, when the photocurable resin composition is applied to the concave surface of the light-transmitting cover member having a shape curved in one direction, the coating thickness of the photocurable resin composition in the vicinity of 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 in the vicinity of the side, and in some cases, the thickness is increased to about several mm. For this reason, in the central part of the concave surface, the curing shrinkage of the photocurable resin composition becomes remarkably large. As a result, a concave is formed in the central part, resulting in a gap in the display surface of the assembled image display device. In addition, there is a problem that color unevenness occurs in the display due to the residual stress of the photo-curing resin layer even if no void is generated.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and an image display member and a curved light-transmitting cover member disposed on the surface side thereof are cured resin of a photocurable resin composition. When manufacturing an image display device by laminating through layers, the display surface of the assembled image display device should be free of voids, and even if no voids are formed, display is performed by the residual stress of the photocurable resin layer. It is intended to prevent color unevenness from occurring.

  The present inventor newly applied a photocurable resin composition to the concave surface of the light-transmitting cover member, pre-cured, and then newly applied a photocurable resin to the recess in the central portion of the temporary-cured resin layer caused by the curing shrinkage. By applying the resin composition, laminating the image display member, and performing the main curing process, it is possible to prevent voids on the display surface of the image display device, and to reduce the residual stress of the photo-curing resin layer. The present inventors have found that color unevenness in display can be prevented and have completed the present invention.

That is, the present invention provides a method for manufacturing an image display device in which an image display member and a curved light-transmitting cover member are laminated via a photo-curing resin layer.
The following steps (A) to (D):
<Process (A)>
Applying the photocurable resin composition to the concave surface of the curved light-transmitting cover member;
<Process (B)>
A step of temporarily curing the applied photocurable resin composition by irradiating with ultraviolet rays to form a temporary cured resin layer having a micro-dent on the concave surface based on the curing shrinkage of the photocurable resin composition;
<Process (C)>
Applying a photocurable resin composition in an amount corresponding to the micro-dents of the temporarily cured resin layer to the temporarily cured resin layer or the image display member;
<Process (D)>
A step of laminating an image display member and a light-transmitting cover member via a temporarily cured resin layer; and <Step (E)>
A step of forming a light-transmitting cured resin layer by irradiating the temporarily-cured resin layer sandwiched between the image display member and the light-transmitting cover member with ultraviolet rays and performing main curing;
A production method is provided.

  In the manufacturing method of the image display device of the present invention, the photocurable resin composition is applied to the concave surface of the curved light-transmitting cover member, subjected to temporary curing treatment, and then the center of the temporary cured resin layer generated by curing shrinkage. A photo-curable resin composition is newly applied to the dent of the part, an image display member is laminated, and a main curing process is performed. For this reason, it is possible to prevent a void from being generated on the display surface of the image display device, and to reduce the residual stress of the photo-curing resin layer, thereby preventing display color unevenness.

FIG. 1A is an explanatory diagram of step (A) of the production method of the present invention. FIG. 1B is an explanatory diagram of the step (A) of the manufacturing method of the present invention. FIG. 1C is an explanatory diagram of a light-transmitting cover member. FIG. 1D is an explanatory diagram of a light-transmitting cover member. FIG. 1E is an explanatory diagram of a light-transmitting cover member. FIG. 1F is an explanatory diagram of a light-transmitting cover member. FIG. 1G is an explanatory diagram of a light-transmitting cover member. FIG. 2A is an explanatory diagram of step (B) of the production method of the present invention. FIG. 2B is an explanatory diagram of the step (B) of the manufacturing method of the present invention. FIG. 3A is an explanatory diagram of step (C) of the production method of the present invention. FIG. 3B is an explanatory diagram of the step (C) of the manufacturing method of the present invention. FIG. 4 is an explanatory diagram of step (D) of the production method of the present invention. FIG. 5 is an explanatory diagram of the step (E) of the production method of the present invention.

  The present invention is a method for manufacturing an image display device in which an image display member and a curved light-transmitting cover member are laminated via a photocurable resin layer, and includes the following steps (A) to (E). It is a manufacturing method. Hereafter, it demonstrates in detail for every process, referring drawings.

<Process (A): Application process>
First, a curved light-transmitting cover member 1 is prepared as shown in FIG. 1A, and the photo-curable resin composition 2 is applied to the concave surface 1a of the light-transmitting cover member 1 with a dispenser D or the like as shown in FIG. 1B. Apply. The coating amount of the photocurable resin composition 2 varies depending on the size, shape, application, etc. of the image display element, but is usually 45 (w) × 80 (l) × 3 (t) mm (radius of curvature (r) : 300 mm) for a curved light-transmitting cover member, when bonding an image display member of 40 (w) × 80 (1) mm in contact with two uncurved sides of the light-transmitting cover member, The thickness of the deepest curved portion is preferably 670 μm at 23.44 cc, and more preferably, a gap of about 100 μm is provided between the two uncurved sides of the light-transmitting cover member and the image display member at 23.76 cc. Is possible. Although this gap depends on the design of the image display device, it is preferably 50 μm or more and 800 μm or less. Moreover, although such an application amount may be satisfied by a single application operation, it may be satisfied by a plurality of application operations.

(Light transmissive cover member 1)
As a specific shape of the curved light-transmitting cover member 1, a shape curved in one direction (for example, a shape on the inferior arc side obtained by cutting a cylindrical pipe along a plane parallel to its central axis (hereinafter referred to as “Yokohama”). (Referred to as a shape)) (FIG. 1A), a shape curved in the X and Y directions (FIG. 1C), a shape curved in the 360 ° direction (for example, obtained by cutting a sphere along a plane not including its center point) For example, the shape of the inferior arc side) (FIG. 1D). The flat part 1b may be formed in the center part of these shapes (for example, FIG. 1E).

  When the light-transmitting cover member 1 has a recumbent shape (FIG. 1A), the inner dam material 3 (FIG. 1F) that defines the application region of the photocurable resin composition on the inner sides of both end portions 1x and 1y, or the It is preferable to provide the outer side dam material 4 (FIG. 1G) which demarcates the application | coating area | region of a photocurable resin composition in the outer side of both ends 1x and 1y. As the inner dam material 3 and the outer dam material 4, the applied photocurable resin composition can be dammed without being compatible with it, and can be easily removed after the photocurable resin composition is temporarily cured. It can be formed from such known materials. For example, as the inner dam material 3, a known thermoplastic elastomer tape provided with a slightly adhesive layer or the like is attached to the inner side of the end of the light-transmitting cover member 1 in a bank shape. Examples of the outer dam material 4 include a silicone sheet and a fluororesin sheet.

  In addition, when the light-transmitting cover member 1 is the embodiment shown in FIGS. 1C and 1D, the dam material may be omitted. Moreover, even in the case of the embodiment of FIGS. 1A and 1B, surface treatment for preventing the flow of the photocurable resin composition on the surface of the light-transmitting cover member 1 corresponding to the inner dam material 3 (for example, Depending on the characteristics of the photocurable resin composition, a roughening treatment, a hydrophilic treatment, a water repellency treatment or the like may be applied.

  The material of the light-transmitting cover member 1 may be light-transmitting so that an image formed on the image display member can be visually recognized. Resins such as glass, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, and polycarbonate Materials. These materials can be subjected to single-sided or double-sided hard coat treatment, antireflection treatment or the like. The dimensional characteristics such as the curved shape and thickness of the light-transmitting cover member 1 and the site competitive physical properties such as elasticity can be appropriately determined according to the purpose of use.

(Photocurable resin composition 2)
The property of the photocurable resin composition 2 applied to the concave surface 1a of the light transmissive cover member 1 is preferably liquid. When a liquid material is used, the photocurable resin composition 2 can be filled in the concave surface 1a of the light transmissive cover member 1 so that the surface of the composition becomes flat. Here, the liquid state means a viscosity of 0.01 to 100 Pa · s (25 ° C.) with a cone plate viscometer.

  Such a photocurable resin composition 2 preferably exemplifies those containing a base component (component (I)), an acrylic monomer component (component (b)), and a photopolymerization initiator (component (c)). can do. If necessary, a plasticizer component (component (d)) can be further contained. The final curing shrinkage of the photocurable resin composition 2 is 3% or more. It may be 5% or more.

  Here, the “final cure shrinkage rate” means a cure shrinkage rate that occurs between the uncured state and the completely cured state of the photocurable resin composition 2. Here, completely cured means a state of being cured so that the curing rate is at least 90% as described later. Hereinafter, the final cure shrinkage rate is referred to as the total cure shrinkage rate. Moreover, the cure shrinkage rate generated between the uncured state and the temporarily cured state of the curable resin composition is referred to as the temporary cure shrinkage rate. Furthermore, 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.

  The total cure shrinkage of the photo-curable resin composition is determined by measuring the specific gravity of the uncured (in other words, before curing) composition and the solid completely cured product after complete curing by an electronic hydrometer (SD manufactured by Alpha Mirage Co., Ltd.). -120L), and can be calculated from the difference in specific gravity between the two by the following formula. In addition, the temporary curing shrinkage ratio of the precured resin of the photocurable resin composition is obtained by calculating the specific gravity of the uncured (in other words, before curing) composition and the solid temporary cured product after the temporary curing with an electronic hydrometer (alpha). Measured using Mirage Co., Ltd. SD-120L), it can be calculated by the following formula from the difference in specific gravity between the two. The main curing shrinkage can be calculated by subtracting the temporary curing shrinkage from the total curing shrinkage.

  The base component of component (a) is a film forming component of the light transmissive cured resin layer, and is a component containing at least one of an elastomer and an acrylic oligomer. Both may be used together as component (A).

  Preferred examples of the elastomer include acrylic copolymers made of acrylic acid ester copolymers, polybutene, polyolefins and the like. In addition, the weight average molecular weight of this acrylate ester copolymer is preferably 5,000 to 500,000, and the repeating number n of polybutene is preferably 10 to 10,000.

  On the other hand, the acrylic oligomer is preferably a (meth) acrylate oligomer having a polyisoprene, polyurethane, polybutadiene or the like as a skeleton. In the present specification, the term “(meth) acrylate” includes acrylate and methacrylate.

  Preferable specific examples of the (meth) acrylate oligomer having a polyisoprene skeleton include an esterified product of a maleic anhydride adduct of polyisoprene polymer and 2-hydroxyethyl methacrylate (UC102 (polystyrene equivalent molecular weight 17000), Kuraray Co., Ltd.) UC203 (polystyrene conversion molecular weight 35000), Kuraray Co., Ltd .; UC-1 (molecular weight about 25000), Kuraray Co., Ltd.) and the like.

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

  As the (meth) acrylate oligomer having a polybutadiene skeleton, a known one can be employed.

  The acrylic monomer component (B) is used as a reactive diluent in the manufacturing process of the image display device in order to impart sufficient reactivity and coating properties to the photocurable resin composition. Examples of such acrylic monomers include 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, stearyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl methacrylate, isobornyl acrylate, Examples include cyclopentanyl acrylate and lauryl methacrylate.

  As the photopolymerization initiator of component (c), a known photoradical polymerization initiator can be used. For example, 1-hydroxy-cyclohexyl phenyl ketone (Irgacure 184, BASF Japan Ltd.), 2-hydroxy -1- {4- [4- (2-Hydroxy-2-methyl-propionyl) benzyl] phenyl} -2-methyl-1-propan-1-one (Irgacure 127, BASF Japan Ltd.), benzophenone, acetophenone, etc. Can be mentioned.

  Such a photopolymerization initiator is insufficiently cured when irradiated with ultraviolet rays if it is too small relative to a total of 100 parts by mass of the acrylic oligomer and acrylic monomer component (b) in the base component (a), and if too large, it is caused by cleavage. Since outgas increases and there exists a tendency of a foaming defect, Preferably it is 0.1-5 mass parts, More preferably, it is 0.2-3 mass parts.

  Moreover, the photocurable resin composition 2 can contain a chain transfer agent for adjusting the molecular weight. Examples thereof include 2-mercaptoethanol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, and α-methylstyrene dimer.

  Moreover, the photocurable resin composition 2 can further contain general additives such as an adhesion improving agent such as a silane coupling agent and an antioxidant, if necessary.

  Since the photocurable resin composition 2 has a cure shrinkage rate of less than 3% in the main curing step after the temporary curing step described later, it is basically essential to contain a plasticizer component. There is no plasticizer component (component (d)) as long as the effect of the present invention is not impaired in order to impart buffering properties to the cured resin layer and reduce the cure shrinkage of the photocurable resin composition. can do. Accordingly, the total content of the base component of component (a) and the acrylic monomer component of component (b) in the photocurable resin composition is preferably 25 to 85% by mass, but the plasticity of component (d) The content of the agent component is in the range of 0 to 65% by mass.

  The plasticizer component (d) does not react with the base component (b) and the acrylic monomer component (b) when irradiated with ultraviolet rays. Such a plasticizer component contains a solid tackifier (1) and a liquid oil component (2).

  Solid tackifiers (1) include terpene resins such as terpene resins, terpene phenol resins and hydrogenated terpene resins, natural rosins, polymerized rosins, rosin esters, rosin resins such as hydrogenated rosins, and terpene hydrogenated resins. Can be mentioned. In addition, a non-reactive oligomer obtained by previously converting the above-mentioned acrylic monomer component into a low molecular weight polymer can also be used. Specifically, a copolymer of butyl acrylate and 2-hexyl acrylate and acrylic acid or cyclohexyl acrylate and Mention may be made of copolymers of methacrylic acid.

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

<Process (B): Temporary curing process>
Next, as shown in FIG. 2A, the applied photocurable resin composition 2 is preliminarily cured by irradiating with ultraviolet rays UV, and is formed on the concave surface 1a of the light-transmitting cover member 1 (usually at the central portion thereof) ) Temporarily cured resin layer 5 having a minute recess 5a based on the curing shrinkage of the photocurable resin composition 2 (for example, an X-shaped recess in FIG. 2B may be a recess having another shape such as a line). To form. “Small” in the minute recess 5a means a volume fluctuation amount due to temporary curing shrinkage. Here, the temporary curing is performed to improve the handleability by making the photocurable resin composition 2 non-flowable. Such a level of temporary curing is such a level that the curing rate (gel fraction) of the temporarily cured resin layer 5 is preferably 10 to 90%, more preferably 40 to 90%. Further, the curing rate (gel fraction) is the ratio of the amount of (meth) acryloyl groups present after ultraviolet irradiation to the amount of (meth) acryloyl groups present in the photocurable resin composition 2 before ultraviolet irradiation (consumption). The amount is defined as “amount ratio”, and the larger the value, the more the curing proceeds.

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

  As long as the curing rate (gel fraction) can be preliminarily cured so that the curing rate (gel fraction) is preferably 10 to 80%, the type of light source, output, accumulated light amount, etc. are not particularly limited, and known ultraviolet irradiation The (meth) acrylate photoradical polymerization process conditions according to can be employed.

  In addition, regarding the ultraviolet irradiation condition, it is possible to select a condition that does not cause dripping or deformation of the temporarily cured resin layer 5 during the bonding operation in the step (C) described later within the range of the curing rate described above. preferable. When expressing such conditions that do not cause dripping or deformation, the viscosity is 20 Pa · S or more (cone plate rheometer, 25 ° C., cone and plate C35 / 2, rotation speed 10 rpm).

  The level of curing in the temporary curing is to cure so that the curing shrinkage rate generated between the temporary cured resin layer 5 and the cured resin layer in the main curing step described later is less than 3%. That is, in the case of the photocurable resin composition 2 having a total cure shrinkage rate of 5%, at least 2% is temporarily cured and contracted during temporary curing.

  In addition, when the inner dam material 3 and the outer dam material 4 are provided in the step (A), the inner dam material 3 or the outer dam material 4 may be removed after the step (B) and before the step (C). preferable. This is because the photocurable resin composition 2 has already been temporarily cured and no resin flow occurs.

<Process (C): Refilling of photocurable resin composition>
Next, an amount of the photocurable resin composition 2 corresponding to the minute recess 5a of the temporarily cured resin layer 5 is applied to the temporarily cured resin layer 5 (FIG. 3A) or the normally flat image display member 6 (FIG. 3B). . Here, the amount corresponding to the minute recess 5a is obtained by measuring the recess shape of the minute recess 5a using a minute surface shape measuring device (for example, 3D measurement laser microscope (OLS4000 series), Shimadzu Corporation). Can be calculated. Or it can also determine with the temporary hardening shrinkage | contraction rate and the usage-amount (volume) of a photocurable resin composition.

  The photocurable resin composition 2 used in this step is preferably the same as the photocurable resin composition 2 used in step (A) from the viewpoint of refractive index, but the refractive index. As long as they are substantially the same, different photocurable resin compositions may be used. Moreover, it is preferable to perform application | coating of a photocurable resin composition so that the photocurable resin composition 2 may be filled into the micro dent 5a by a conventionally well-known method. For example, when the photocurable resin composition 2 is applied to the temporarily cured resin layer 5 or the image display member 6, a line shape (FIGS. 3A and 3B), an X shape, or a dot in the center so as to fill the minute recess 5a. What is necessary is just to apply | coat.

  Even when the application position of the photocurable resin composition 2 is shifted from the minute recess 5a, the applied photocurable resin composition 2 is vacuum-applied while maintaining fluidity without being temporarily cured. Therefore, the photocurable resin composition 2 can be appropriately moved to the minute recess 5a.

  Examples of the image display member 6 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.

  As a preferred embodiment of the step (B) and the main step (C) described above, in the step (B), a micro-dent is generated at least in the central portion of the concave surface of the light-transmitting cover member, and the step (C ), A mode in which a photocurable resin composition corresponding to 70% or more of the micro-dent volume is applied to the corresponding temporarily cured resin layer or image display member.

<Process (D): Lamination process>
Subsequently, the image display member 6 and the light-transmitting cover member 1 are laminated via the temporarily cured resin layer 5 (FIG. 4). Lamination can be performed by applying pressure at 10 ° C. to 80 ° C. using a known pressure bonding device, but there are bubbles between the temporarily cured resin layer 5 and the image display member 6 or the light-transmitting cover member 1. In order not to enter, it is preferable to perform lamination by a so-called vacuum bonding method.

  In addition, after a process (D), before a process (E), a well-known pressurization defoaming process (example of process conditions: 0.2-0.8 MPa, 25-60 degreeC, 5-20min) is performed to a laminated body. Preferably it is done.

<Process (E): Main curing process>
Subsequently, the light-curing cured resin layer 7 is formed by irradiating the UV-cured UV light onto the temporarily cured resin layer 5 sandwiched between the image display member 6 and the light-transmitting cover member 1 to perform main curing (see FIG. FIG. 5). Thereby, the target image display apparatus is obtained. The main curing in this step is to sufficiently cure the temporarily cured resin layer 5 and bond and laminate the image display member 6 and the light-transmitting cover member 1. Such a level of main curing is such that the curing rate (gel fraction) of the light-transmitting cured resin layer 7 is preferably 90% or more, more preferably 95% or more.

  The light transmissive level of the light transmissive cured resin layer 7 may be light transmissive so that an image formed on the image display member 6 can be visually recognized.

  Hereinafter, the present invention will be specifically described by way of examples. In the following examples, the total cure shrinkage, temporary cure shrinkage, and main cure shrinkage of the photocurable resin composition are the specific gravity of the photocurable resin composition, the precured product, and the completely cured product, respectively. The specific gravity was measured using an electronic hydrometer (SD-120L manufactured by Alpha Mirage Co., Ltd.), and the measurement results were applied to the following equation.

Comparative Example 1
(Process (A): Application process))
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 (r) is 300 mm in the width direction. A resin cover (FIG. 1A) was obtained as a curved recumbent light-transmitting cover member.

  Separately, 50 parts by mass of (meth) acrylic oligomer having a polybutadiene skeleton (TE-2000, Nippon Soda Co., Ltd.), 20 parts by mass of hydroxyethyl methacrylate, 10 parts by mass of a photopolymerization initiator (Irgacure 184, BASF Japan Ltd.) 3 parts by mass, 7 parts by mass of SpeedCure TPO and DKSH Japan Co., Ltd.) were uniformly mixed to prepare a photocurable resin composition. This photocurable resin composition exhibited a total cure shrinkage of 5.6% between a cure rate of 0% and 90%.

  Next, both ends of the recumbent resin cover were sandwiched between two silicone rubber sheets as outer dam materials (FIG. 1G). The prepared photocurable resin composition was discharged into the concave portion of the resin cover by using a resin dispenser so that the thickness at the center was 880 μm, thereby forming a photocurable resin composition film.

(Process (B): Temporary curing process)
Next, an intensity of 200 mW / cm ^{2 is} applied to the photocurable resin composition film using an ultraviolet irradiation device (LC-8, Hamamatsu Photonics Co., Ltd.) so that the integrated light amount becomes 1200 mJ / cm ^2. The photocurable resin composition film was temporarily cured by irradiating the ultraviolet ray of 6 seconds to form a temporarily cured resin layer, and the outer dam material was further removed. During the temporary curing, it was observed that a minute concave portion was formed in the central portion of the temporary cured resin layer (FIG. 2B). The temporary curing shrinkage percentage was 3.8%.

In addition, when the hardening rate of the temporary hardening resin layer was calculated | required using the absorption peak height of 1640-1620 cm < ^-1 > from the base line in a FT-IR measurement chart as a parameter | index, it was about 70%.

(Process (D): Lamination process)
Next, the light-transmitting cover member obtained in the step (B) is placed on the surface where the polarizing plate of the flat liquid crystal display element having a size of 40 (W) × 80 (L) mm is laminated. It mounted so that it might become the polarizing plate side, and it affixed with the vacuum bonding machine (The vacuum degree 50Pa, the bonding pressure 0.07MPa, the bonding time 3 seconds, normal temperature) from the resin cover side (FIG. 4).

(Process (E): Main curing process)
Next, with respect to the liquid crystal display device, a resin cover side, by irradiating ultraviolet irradiation device ultraviolet using (ECS-03601EG, Eye Graphics Co.) the (200 mW / cm ²⁾ at 3000 mJ / cm ² The temporarily cured resin layer was completely cured to form a light transmissive cured resin layer. The curing rate of the light transmissive cured resin layer was 98%. As a result, a liquid crystal display device was obtained in which a curved resin cover as a light-transmitting cover member was laminated on the liquid crystal display element via the light-transmitting cured resin layer. Further, the main curing shrinkage percentage was 1.8%.

  The resulting liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids. As a result, a bubble-like void was generated at the approximate center of the interface between the light-transmitting cured resin layer and the liquid crystal display element.

Comparative Example 2
As a photocurable resin composition, 40 parts by mass of a (meth) acrylate oligomer having a polyisoprene skeleton (UC203, Kuraray Co., Ltd.), 20 parts by mass of dicyclopentenyloxyethyl methacrylate (FA512M, Hitachi Chemical Co., Ltd.) Hydroxypropyl methacrylate (HPMA, Nippon Kasei Chemical Co., Ltd.) 3 parts by mass, tetrahydrofurfuryl acrylate (light ester THF, Kyoeisha Chemical Co., Ltd.) 15 parts by mass, lauryl acrylate (light ester L, Kyoeisha Chemical Co., Ltd.), 20 parts by mass of a polybutadiene polymer (Polyoil 110, Evonik Japan Co., Ltd.), 45 parts by mass of a hydrogenated terpene resin (P85, Yasuhara Chemical Co., Ltd.), 4 parts by mass of a photopolymerization initiator (Irgacure 184, BASF Japan Co., Ltd.) Prepared by blending uniformly The liquid crystal display device was operated in the same manner as in Comparative Example 1 except that the photo-curable resin composition (with a curing rate of 0% to 90% and a total curing shrinkage of 3.4%) was used. Obtained.

  About the obtained liquid crystal display device, when the presence or absence of the occurrence of voids was visually observed from the resin cover side, no voids were observed at the interface between the liquid crystal display device (polarizing plate) and the light transmissive cured resin layer, When the display operation was performed, color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.1%, and the main curing shrinkage rate was 0.3%.

Comparative Example 3
As a photocurable resin composition, 6 parts by mass of polyisoprene methacrylate (UC102, Kuraray Co., Ltd.) as a radical photopolymerizable poly (meth) acrylate, 15 parts by mass of dicyclopentenyloxyethyl methacrylate as a reactive diluent and lauryl methacrylate 5 parts by mass, 20 parts by mass of polybutadiene (Polybest 110, Evonik Japan Co., Ltd.) as a plasticizer, 1 part by mass of a photopolymerization initiator (Irgacure 184, BASF Japan Ltd.), and hydrogenated terpene resin (Clearon) as a tackifier M105, Yasuhara Chemical Co., Ltd.) a photo-curable resin composition prepared by uniformly blending 53 parts by mass (showing a total cure shrinkage of 2.6% between 0% and 90% cure rate). The liquid crystal display device was operated in the same manner as in Comparative Example 1 except that it was used. It was.

  About the obtained liquid crystal display device, when the presence or absence of the occurrence of voids was visually observed from the resin cover side, no voids were observed at the interface between the liquid crystal display device (polarizing plate) and the light transmissive cured resin layer, When the display operation was performed, color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 2.2%, and the main curing shrinkage rate was 0.4%.

Example 1
Between step (B) and step (D) in Comparative Example 1, as the step (C), an amount of the photocurable resin composition corresponding to the slight depression of the temporarily cured resin layer (the step (A in Comparative Example 1) The same composition as that used in the above) was used in the same manner as in Comparative Example 1 except that the resin dispenser used in Comparative Example 1 was used and applied in a line to the central portion of the temporarily cured resin layer. A liquid crystal display device was obtained. The amount corresponding to the minute dents of the temporarily cured resin layer of the photocurable resin composition was measured by the amount (volume) of the photocurable resin composition and the temporary curing shrinkage rate, and the amount was 0.91 cc. It was.

  With respect to the obtained liquid crystal display device, when the presence or absence of voids was visually observed from the resin cover side, no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage was 3.8%, and the main curing shrinkage was 1.8%.

Example 2
Between step (B) and step (D) in Comparative Example 1, as the step (C), an amount of the photocurable resin composition corresponding to the slight depression of the temporarily cured resin layer (the step (A in Comparative Example 1) The same composition as that used in the above) was used in the same manner as in Comparative Example 1 except that the resin dispenser used in Comparative Example 1 was used and applied in a line to the central portion of the temporarily cured resin layer. A liquid crystal display device was obtained. In addition, although the quantity corresponding to the micro dent of the temporary hardening resin layer of a photocurable resin composition was 0.91cc when it measured by the usage-amount (volume) and temporary hardening shrinkage rate of the photocurable resin composition. Then, a 0.64 cc photocurable resin composition corresponding to about 70% was applied.

  The resulting liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids. Almost no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage was 3.8%, and the main curing shrinkage was 1.8%.

Example 3
Between the step (B) and the step (D) in Comparative Example 2, as the step (C), an amount of the photocurable resin composition corresponding to the slight depression of the temporarily cured resin layer (the step (A in Comparative Example 1) The same composition as that used in the above) was used in the same manner as in Comparative Example 1 except that the resin dispenser used in Comparative Example 1 was used and applied in a line to the central portion of the temporarily cured resin layer. A liquid crystal display device was obtained. The amount corresponding to the minute dents of the temporarily cured resin layer of the photocurable resin composition is measured by the amount (volume) of the photocurable resin composition and the temporary curing shrinkage, and the amount is about 0.74 cc. there were.

  With respect to the obtained liquid crystal display device, when the presence or absence of voids was visually observed from the resin cover side, no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.1%, and the main curing shrinkage rate was 0.3%.

Example 4
Between step (B) and step (D) in Comparative Example 3, as the step (C), an amount of the photocurable resin composition corresponding to the slight depression of the temporarily cured resin layer (the step (A in Comparative Example 1) ) Except that the same composition as that used in step 1) was applied to the liquid crystal display element side of the portion corresponding to the line shape at the center of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. A liquid crystal display device was obtained by the same operation as in Comparative Example 1. In addition, the amount corresponding to the minute dents of the temporarily cured resin layer of the photocurable resin composition is measured by the usage amount (volume) of the photocurable resin composition and the temporary curing shrinkage, and the amount is 0.53 cc. there were.

  With respect to the obtained liquid crystal display device, when the presence or absence of voids was visually observed from the resin cover side, no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 2.2%, and the main curing shrinkage rate was 0.4%.

  In the manufacturing method of the image display device of the present invention, the photocurable resin composition is applied to the concave surface of the curved transparent cover member, subjected to temporary curing treatment, and then the central portion of the temporary cured resin layer generated by curing shrinkage. A photocurable resin composition is newly applied to the dent, an image display member is laminated, and a main curing process is performed. For this reason, it is possible to prevent a void from being generated on the display surface of the image display device, and to reduce the residual stress of the photo-curing resin layer, thereby preventing display color unevenness. Therefore, the production method of the present invention is useful for industrial production of an in-vehicle information terminal equipped with a touch panel.

DESCRIPTION OF SYMBOLS 1 Light-transmitting cover member 1a Recessed surface 1x, 1y both ends of a light-transmitting cover member 2 Photocurable resin composition 3 Inner dam material 4 Outer dam material 5 Temporarily cured resin layer 5a Small dent 6 Image display member 7 Light transmission Cured resin layer D Dispenser

Claims (11)

In the manufacturing method of the image display device in which the image display member and the curved light-transmitting cover member are laminated via the photocurable resin layer,
The following steps (A) to (D):
<Process (A)>
Applying the photocurable resin composition to the concave surface of the curved light-transmitting cover member;
<Process (B)>
A step of temporarily curing the applied photocurable resin composition by irradiating with ultraviolet rays to form a temporary cured resin layer having a micro-dent on the concave surface based on the curing shrinkage of the photocurable resin composition;
<Process (C)>
Applying a photocurable resin composition in an amount corresponding to the micro-dents of the temporarily cured resin layer to the temporarily cured resin layer or the image display member;
<Process (D)>
A step of laminating an image display member and a light-transmitting cover member via a temporarily cured resin layer; and <Step (E)>
A step of forming a light-transmitting cured resin layer by irradiating the temporarily-cured resin layer sandwiched between the image display member and the light-transmitting cover member with ultraviolet rays and performing main curing;
A manufacturing method comprising:   The manufacturing method according to claim 1, wherein the light-transmitting cover member used in the step (A) has a recumbent shape.   In step (B), a micro-dent is generated at least in the center of the concave surface of the light-transmitting cover member, and a photocurable resin composition corresponding to 70% or more of the micro-dent volume in step (C) is supported. The manufacturing method of Claim 1 or 2 apply | coated to the temporary-hardening resin layer or image display member to perform.   The production according to claim 2 or 3, wherein an inner dam member or an outer dam member that defines an application region of the photocurable resin composition is provided on the inner side or the outer side of both ends of the light-transmitting cover member. Method.   The manufacturing method of Claim 4 which removes an inner side dam material or an outer side dam material between a process (B) and a process (C).   The manufacturing method in any one of Claims 1-5 which laminates | stacks a process (D) by a vacuum bonding method.   The manufacturing method in any one of Claims 1-6 which performs a pressure defoaming process between a process (D) and a process (E).   The manufacturing method 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 process according to any one of claims 1 to 8, wherein in the step (B), the photocurable resin composition is preliminarily cured by irradiating with ultraviolet rays so that the curing rate of the temporarily cured resin layer is 10 to 90%. Method.   The manufacturing method according to any one of claims 1 to 9, wherein in the step (E), the temporarily cured resin layer is irradiated with ultraviolet rays so that the curing rate of the light transmissive cured resin layer is 90% or more. . The photocurable resin composition is a liquid resin composition containing at least one of an elastomer and an acrylic oligomer, an acrylic monomer, and a photopolymerization initiator,
The elastomer is at least one selected from the group consisting of acrylic copolymers, polybutenes and polyolefins;
The method according to any one of claims 1 to 10, wherein the acrylic oligomer is at least one selected from the group consisting of polyurethane (meth) acrylate, polybutadiene (meth) acrylate, and polyisoprene (meth) acrylate. .

Images