JP2014106305A - Display device, and manufacturing method of display device - Google Patents

Abstract

Provided is a technique capable of preventing and suppressing damage such as contraction of a member side (an element such as a polarizing plate) due to the effect of light irradiation for photocuring on a photocurable adhesive.
In a method for manufacturing a display device having a structure in which a display panel and a transparent cover are bonded together with a photocurable adhesive 8, the ratio of absorbance per wavelength in a polymerization initiator 81 contained in the photocurable adhesive 8 is obtained. When the absorbance at a wavelength of 365 nm is 1, the wavelength is 365 nm: wavelength 405 nm = 1: (0.25 to 0.5).
[Selection] Figure 5

Description

  The present invention relates to a technology such as a display device and an adhesive.

  As a display device in which members are bonded using an adhesive, there are many display devices in which a surface such as a transparent cover or a touch panel (also referred to as a touch sensor) is bonded to the surface of the display panel. For example, there is a liquid crystal display device (abbreviated as LCD) including a liquid crystal display panel. For example, a transparent cover is bonded to the entire display area of a flat panel with an adhesive.

  A transparent cover made of, for example, tempered glass or acrylic resin is often disposed on the viewer side (front side) of the LCD panel. This transparent cover is a layer having a role of a protective cover plate or the like. Other roles (functions) include optical filters (such as transmittance adjustment and reflection suppression), and antistatic.

  In recent years, with the enhancement of functions of mobile phone terminals, tablet computers, etc., the transparent cover layer is often replaced with a touch panel (touch sensor) layer. For example, many portable terminals equipped with a liquid crystal touch panel are provided. Note that the touch panel includes a resistance film method, an ultrasonic method, a capacitance method, and the like.

  Examples of the adhesive for bonding the members include a photo-curing adhesive, a transparent adhesive sheet, a sheet in which silicone gel and silicone rubber are laminated, and the like. In particular, recently, a photo-curing adhesive that is a type that is cured by light such as ultraviolet rays (UV) has been widely used.

  The transparent cover is disposed at a predetermined distance from the panel surface via an adhesive according to the predetermined function. Therefore, an air layer may be interposed between the transparent cover surface and the panel surface. In this case, unnecessary interface reflection occurs at the interface with the air layer due to the difference in refractive index, which causes a decrease in display contrast.

  In a configuration in which a transparent cover is bonded to the panel surface, as a measure for the air layer, a configuration in which the refractive index of the adhesive layer is adjusted using a transparent adhesive layer such as the photo-curing adhesive or the transparent adhesive sheet. Is used. That is, the refractive index of the adhesive layer is adjusted to be equal to the refractive index of the transparent cover.

  When using a sheet-like member such as a transparent adhesive sheet or a sheet in which silicone gel and silicone rubber are laminated as means for laminating the above-mentioned members, it is only about 60% of the thickness of the sheet at the time of adhesion. Since it does not deform, air bubbles may be generated in the bonded portion. For example, in the module of the display device, there may be a step in the printing portion in a portion (cover) on which printing with a film thickness of about several hundred μm is performed for the design of the peripheral portion. In the case of adhesion by the sheet-like member, there is a manufacturing problem that the step cannot be absorbed and bubbles are generated. Therefore, a manufacturing method using a photo-curing adhesive instead of the transparent adhesive sheet or the like is becoming mainstream.

  When a photocurable adhesive is used as means for bonding the above members (for example, an LCD panel and a transparent cover), an outline of the manufacturing process (bonding step) is as follows, for example. (1) An adhesive (photocurable adhesive) is applied to the surface of the panel or transparent cover. (2) The panel and the transparent cover are arranged so as to face each other so that the adhesive application surface is on the inside, and they are gradually brought closer to each other so that the application surface is in contact with the other surface. . At this point, the adhesive is in an uncured state. (3) A light beam is irradiated from the light source to the laminated member (panel, adhesive, transparent cover) from the transparent cover side. That is, the adhesive is cured by irradiating the light curable adhesive with light rays, and the members are bonded to each other. At this point, the adhesive is cured and transparent.

  As a typical light source and irradiation device for curing the photo-curable adhesive, a high-pressure mercury ultraviolet lamp (hereinafter also referred to as “halogen lamp” as appropriate) and an ultraviolet irradiation device are often used. The corresponding photocurable adhesive is also referred to as an ultraviolet (UV) curable adhesive.

  The high pressure mercury ultraviolet lamp has a dominant wavelength at a wavelength of 365 nm (described later in FIG. 7). Therefore, it is preferable to use a photocurable adhesive mainly having a high sensitivity or absorbance near a wavelength of 365 nm (a mixture of a polymerization initiator having a high sensitivity or absorbance near a wavelength of 365 nm).

  In addition, in the process of stacking (lamination) of members using the above-mentioned photo-curing adhesive, it is necessary to prevent abnormalities after lamination, for example, residual bubbles or contamination of minute foreign matters. If it is discovered before the adhesive is cured, it can be dealt with. That is, the panel and the transparent cover are peeled off, and the adhesive containing the abnormality is temporarily removed. Then, it is possible to apply (rework) an adhesive again between the panel and the transparent cover.

  With respect to a display device in which members are bonded using the above-mentioned adhesive, examples of prior art include Japanese Unexamined Patent Application Publication No. 2009-93200 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2008-216543 (Patent Document 2).

  Patent Document 1 (“display device” and the like) describes “providing a display device that can improve the strength of the touch panel and can reduce the thickness of the display device”. . Patent Document 1 describes that a liquid crystal display panel and a touch panel are bonded together with a resin filler (a transparent resin filler that is cured by irradiating a polymerizable resin composition with ultraviolet rays).

  Patent Document 2 (“Organic Electroluminescence Device with Input Function”, etc.) describes “Providing an organic EL device with an input function that can achieve high detection accuracy and has high performance and high reliability”. ing. In Patent Document 2, the element substrate 11 and the sealing substrate 12 are bonded together by the sealing resin 13. The sealing resin 13 is made of a thermosetting resin, an ultraviolet curable resin, or the like. Has been. Patent Document 2 also describes a touch panel, an ultraviolet curable resin, and the like.

JP 2009-93200 A JP 2008-216543 A

  As described above, for a display device in which the surface of a panel such as an LCD and the surface of a layer such as a transparent cover or a touch panel are bonded together with a photo-curing adhesive, photo-curing adhesion after the members are stacked (laminated) For curing the agent, a high-pressure mercury ultraviolet lamp or the like is used as a light source and an irradiation device. The halogen lamp has a dominant wavelength at a wavelength of 365 nm.

  On the other hand, when the display device is an LCD, polarizing plates that are optical polarizers are provided on the front and back surfaces of the LCD panel. The polarizing plate has a structure in which, for example, a polarizer composed of a polyvinyl alcohol (PVA) film drawn by adsorbing iodine (I) is protected from both sides by a triacetyl cellulose (TAC) film. That is, the TAC film is provided as a protective layer that protects the PVA film, which is a polarizer that easily contracts due to external ultraviolet rays and humidity.

  When manufacturing a module having a structure in which an LCD panel including the polarizing plate and a transparent cover are bonded together using a UV curable adhesive, the module is bonded by irradiating with UV rays for curing the adhesive. The light beam is also irradiated to the polarizing plate through the agent. Thereby, the polarizing plate itself absorbs UV and contracts. In particular, the PVA layer absorbs and contracts the UV component that could not be absorbed and shielded by the TAC layer (transmitted). That is, the polarization axis shift as a polarizer occurs as damage due to contraction of the polarizing plate (mainly PVA layer). This causes a problem that the display quality of the LCD is lowered.

  Regarding the above-mentioned problem, FIG. 8 shows a graph in which the absorbance for each wavelength in the LCD polarizing plate having a conventional structure is measured. The absorbance here is a value for the entire polarizing plate. As shown in the figure, it can be seen that the polarizing plate has a high degree of absorption of light having a wavelength of around 400 nm (line a) or less.

The light absorbency is a dimensionless amount that represents the degree to which the intensity decreases when light passes through an object, and is a negative value obtained by taking the common logarithm of transmittance. Absorbance: A = −log (I / I ₀ ), I: transmitted light intensity, I ₀ : incident light intensity.

  In view of the above, the main object of the present invention is the influence of light irradiation for photocuring on a photocurable adhesive with respect to a display device in which members (display panel and transparent cover, etc.) are bonded together using an adhesive. It is to provide a technique capable of preventing / suppressing damage such as contraction on the member side (element such as a polarizing plate).

  In order to achieve the above object, a representative embodiment of the present invention is a display device in which members (display panel and transparent cover, etc.) are bonded together using an adhesive, a manufacturing method thereof, an adhesive, and the like. It has the structure shown below, It is characterized by the above-mentioned.

  (1) The present embodiment is a display device in which a display panel and a transparent cover are bonded together using an adhesive, and the adhesive is a photo-curing adhesive including a polymerization initiator, When the first wavelength in the irradiation light for photocuring of the adhesive is around 365 nm and the second wavelength is around 405 nm, the polymerization initiator has a first wavelength: a second wavelength = 1: (0.25 to 0.5).

  (2) Further, when the third wavelength in the irradiation light for photocuring of the adhesive is set to around 435 nm, the polymerization initiator has a first wavelength: third wavelength = 1 as a ratio of absorbance for each wavelength. : (0 to 0.1).

  (3) The adhesive comprises monomers and oligomers that are positively polymerized by the polymerization initiator.

  According to a typical embodiment of the present invention, the influence of light irradiation for photocuring on a photocurable adhesive with respect to a display device in which members (display panel and transparent cover, etc.) are bonded together using an adhesive. It is possible to prevent / suppress damage such as shrinkage on the member side (elements such as polarizing plates) due to. Thereby, for example, it is possible to prevent / suppress display quality deterioration due to deviation of the polarization axis in an element such as a polarizing plate.

It is a figure which shows the cross-section of the principal part of the display apparatus (LCD module) of one embodiment of this invention. It is a figure which shows the structure before adhesion | attachment (separation) of each member of the display apparatus of FIG. It is a figure which shows schematically the irradiation of the light ray (UV) with respect to the photocurable adhesive agent and deflection | deviation board (enlargement) in this Embodiment. It is a figure which shows the manufacturing process of the manufacturing method of the display apparatus of one embodiment of this invention. It is a figure which shows a composition, characteristic, etc. of the photocurable adhesive agent in this Embodiment. It is a figure which shows the relationship of each wavelength in the vicinity of the boundary area | region of visible light and UV. It is explanatory drawing which shows the outline (principal wavelength etc.) of the spectral distribution of the example (high pressure mercury ultraviolet lamp) of a light source. It is a figure which shows the measurement data of the light absorbency of the polarizing plate for LCD of the conventional structure. It is a figure which shows roughly the example of the system of the light irradiation in the manufacturing method of the display apparatus of Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted. In addition, in the drawings, cross-sectional hatching and the like are omitted as appropriate for easy understanding, and the main parts are shown with emphasis and actual dimensions and ratios are different. Further, in this specification, the term “process” is not limited to an independent process, and the term “process” is used as long as the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. It is included in the “process”. For the sake of explanation, the in-plane direction corresponding to the panel screen is the XY direction, and the vertical direction is the Z direction.

<Summary>
In the display device of this embodiment, a surface of a panel, for example, a surface of a polarizing plate that is a component of the panel (or an element connected to the panel) and a surface of a transparent cover or the like are attached using a photocurable adhesive. It is a structure to match (adhere). Further, the method for manufacturing a display device according to the present embodiment includes a manufacturing process in which a surface of a panel, for example, a surface of a polarizing plate that is a component of the panel and a surface such as a transparent cover are bonded using a photocurable adhesive. . The transparent cover may be a transparent plate or transparent layer mainly made of glass or organic glass, or may be a transparent touch panel or touch sensor layer. In the case of the touch panel layer, for example, a transparent electrode made of ITO or the like is included.

  In the above structure and manufacturing process, the adhesive (photocurable adhesive) has a first wavelength and a second wavelength when the first wavelength (w1) = 365 nm and the second wavelength (w2) = 405 nm with respect to the absorbance. A polymerization initiator in which the ratio or ratio of the absorbance in w1 is w1 (365 nm): w2 (405 nm) = 1: (0.25-0.5), and monomers and oligomers that are positively polymerized by the polymerization initiator Comprising.

  For example, the adhesive includes a polymerization initiator having an absorbance ratio of wavelength 365 nm (w1): wavelength 405 nm (w2) = 1: 0.5, and monomers and oligomers that are positively polymerized by the polymerization initiator. Comprising.

  In the present specification, the numerical range indicated as “a-b” using the above “to” includes the numerical values (a, b) before and after “to” as the minimum value and the maximum value. Indicates a range (a ≦ X ≦ b) (X is an arbitrary value within the range). For example, when w1: w2 = 1: 0.5, it indicates that the absorbance at w2 = 405 nm is ½ of the absorbance at w1 = 365 nm.

  The meanings of the numerical values of the adhesive conditions are as follows. Conventionally, the w1 absorbance is large and the w2 absorbance is small at w1: w2 (w1: w2 = 1: (0 to 0.1)), but in the present invention and the embodiment, the absorbance of w2 is increased with respect to w1 ( w1: w2 = 1: (value greater than 0.1)). This reduces the irradiation time or irradiation amount required for curing the adhesive. Thereby, the (total) irradiation time or irradiation amount irradiated to the polarizing plate is reduced, and shrinkage damage can be suppressed.

  The first wavelength (w1) = 365 nm is selected corresponding to the main purpose of photocuring of the adhesive and corresponding to the characteristics of the main wavelength of a halogen lamp or the like serving as a light source for light irradiation. In addition, since the polarizing plate has a high absorbance at a wavelength of about 400 nm or less as described above, it is possible to prevent or suppress the influence on an element such as a polarizing plate by absorbing a component having a wavelength of about 400 nm or less with an adhesive layer.

  The second wavelength (w2) = 405 nm corresponds to the purpose of preventing or suppressing the influence on the polarizing plate or the like due to the light irradiation component that transmits the adhesive quickly by light curing the adhesive. The selection is made according to the characteristics of the sub-wavelength.

  The lower limit 0.25 of the absorbance range of w2 in the above ratio is required to be at least 0.2 as the absorbance at which the photocuring reaction occurs at w2, so 0.25 is the lower limit in consideration of the likelihood. Is selected.

  The upper limit value 0.5 of the absorbance range of w2 in the above ratio is selected in accordance with the upper limit value of the absorbance of w2 of the photocurable adhesive / polymerization initiator currently produced and marketed.

  Further, in the above structure and manufacturing process, the adhesive (photo-curing adhesive) has a first wavelength (w1) = 365 nm, a second wavelength (w2) = 405 nm, and a third wavelength (w3) = 435 nm with respect to the absorbance. In this case, the absorbance at a wavelength of the third wavelength or longer is set to a sufficiently small value. For example, it comprises a polymerization initiator in which the ratio or ratio of absorbance at the first wavelength and the third wavelength is w1 (365 nm): w3 (435 nm) = 1: (0 to 0.1). Thereby, the degree to which the adhesive reacts (absorbs) with visible light is reduced, and the ease of the manufacturing process and transparency are increased.

  In particular, the manufacturing method of the display device is such that the panel (polarizing plate), the photo-curing adhesive, the transparent cover, and the like are overlaid (laminated), and the adhesive is irradiated with light including ultraviolet rays. And bonding them together. Thereby, the adhesive (its polymerization initiator) absorbs the first wavelength (w1) in the irradiation light well and initiates / promotes the photocuring reaction. At the same time, the adhesive (its polymerization initiator) absorbs the second wavelength (w2) of the irradiated light at a rate of about 1/4 to 1/2 of the first wavelength (w1). As a result, the photo-curing reaction of the adhesive is further promoted (moves faster), the time required for curing is shortened, and the total irradiation time and irradiation amount for bonding are less than before. Thereby, the total irradiation time and the amount of irradiation in which the irradiation light that could not be absorbed / shielded by the adhesive (transmitted) is irradiated to the deflecting plate of the panel or the like is reduced. Thereby, the influence (damage by shrinkage | contraction) to the deflection plate etc. of a panel can be suppressed. That is, it is possible to prevent / suppress deterioration of the polarization axis of the deflecting plate and to secure display quality.

<Embodiment 1>
The display device and the manufacturing method thereof according to the first embodiment of the present invention will be described with reference to FIGS.

[Display device (LCD)]
FIG. 1 shows a cross-sectional structure of an LCD (also referred to as an LCD module) 10 that is a display device of the present embodiment, and shows a state after the members are bonded together. The cross-sectional shape is substantially the same as that of a conventional LCD, and the dimensions and ratios of the mounting are appropriately designed.

  The display device (LCD) 10 has a configuration in which an LCD panel 9 including polarizing plates 4 and 5 and a transparent cover 7 are bonded with an adhesive (photo-curing adhesive) 8. The LCD panel 9 has, as a basic structure, a first substrate 1 and a second substrate 2 that are disposed to face each other, and a liquid crystal layer 6 is sandwiched and sealed between the substrates (1, 2). It is the structure bonded together through the sealing material 3. The first substrate 1 and the second substrate 2 are made of an insulating transparent substrate structure made of, for example, glass or organic glass (acrylic resin or polycarbonate). The first substrate 1 on the back side is a TFT array substrate on which TFTs (thin film transistors) and the like are formed. The second substrate 2 on the front side is an observer side and is a CF substrate on which a color filter (CF) or the like is formed. The sealing material 3 is formed in a peripheral portion (or frame portion) outside the display region (screen) of the LCD panel 9 so as to surround the liquid crystal layer 6 in a plan view (XY).

  Polarizing plates (4, 5) are attached to the outer surfaces of the substrates (1, 2) before and after the LCD panel 9. That is, the first polarizing plate 4 is connected to the first substrate 1 on the back side, and the second polarizing plate 5 is connected to the second substrate 2 on the front side. The surface of the transparent cover 7 is bonded to the surface of the polarizing plate 5 on the front side of the LCD panel 9 with an adhesive 8.

  FIG. 2 shows a configuration of separation (before bonding) of each part (LCD panel 9, transparent cover 7, adhesive 8) of the display device (LCD) 10 of the present embodiment corresponding to FIG. The surface f1 of the polarizing plate 5 of the LCD panel 9 and the surface f4 of the transparent cover 7 are bonded with an adhesive 8 (connection surfaces f2, f3). The surfaces f1 and f4 to be bonded (bonded) are, for example, the entire surface corresponding to the display area.

[Transparent cover]
The transparent cover 7 is made of a material having transparency (visible light transparency) such as glass or acrylic resin, and serves as a protective cover for preventing the LCD panel 9 from being damaged, and the color tone of the entire display device 10. It plays a role as a correction plate (optical filter). In addition, a predetermined function such as an antistatic layer can be provided. The thickness of the transparent cover 7 in the Z direction is not particularly limited, but is preferably 0.5 to 2.5 mm, for example, and is 1.6 mm in this example.

  As another embodiment, the transparent cover 7 may be replaced with a transparent touch panel (or touch sensor) layer.

[Light irradiation on adhesive and polarizing plate]
FIG. 3 schematically shows a light irradiation (UV irradiation) with respect to the photocurable adhesive 8 in the display device 10 of the present embodiment, a structural example of the polarizing plate 5 and the like. The irradiation device 300 includes, for example, a high-pressure mercury ultraviolet lamp as a light source. At the time of manufacture, light including UV is irradiated from the irradiation device 300 to the adhesive 8 of the LCD 10 (the adhesive 8 in a state where the respective parts in FIG. 2 are laminated). The adhesive 8 is photocured and adhered by irradiation light including UV. Irradiation light including UV is irradiated not only on the adhesive 8 but also on the polarizing plate 5 through its transmission.

  For example, the polarizing plate 5 is mainly composed of a PVA (polyvinyl alcohol) film layer (PVA layer 52) as a polarizer, and a TAC (triacetylcellulose) film layer (TAC layer 51) serving as a protective layer on the front and back surfaces thereof. , 53) are laminated and bonded together.

  The PVA layer 52 is a polarizer made of a PVA film stretched by adsorbing iodine (I), and constitutes a predetermined polarization axis related to liquid crystal display. The PVA layer 52 (especially iodine (I)) easily absorbs (absorbs) external UV light, that is, light having a wavelength of about 400 nm or less, and is easily damaged by contraction due to the light absorption. As a result, as described above, there is a problem that leads to deterioration such as deviation of the polarization axis (described later in FIG. 6).

  The TAC layers (51, 53) are provided as a protective layer for protecting the PVA layer 52 that is easily contracted by the UV and humidity. That is, the TAC layers (51, 53) have a property of absorbing or blocking UV (wavelength of about 400 nm or less) in accordance with the characteristics of the PVA layer 52. As the thickness of the TAC layers (51, 53) increases in the Z direction, the protection performance for the PVA layer 52 increases. On the other hand, there is a demand / trend for making the module thinner, and when the thickness of the polarizing plate 5 or its TAC layer (51, 53) in the Z direction is reduced, the protection performance is lowered.

  Note that a PET (polyethylene terephthalate) layer may be provided as the outermost protective layer of the polarizing plate 5 in the LCD panel 9, but this is not provided in the present embodiment.

[Manufacturing method of display device]
FIG. 4 shows a process outline in a method for manufacturing the display device (LCD) 10 of the first embodiment. S1 and the like indicate steps or processes. The configuration of the adhesive 8 to be used will be described later.

  In S1, portions (1, 2, 3) excluding the polarizing plates 4, 5 in the LCD panel 9 of FIG. 2 are manufactured or prepared.

  In S2, polarizing plates 4 and 5 are manufactured or prepared. The polarizing plate 5 has, for example, the configuration shown in FIG.

  In S3, the polarizing plates 4 and 5 of S2 are attached to the front and back surfaces of the LCD panel 9 of S1. For example, the LCD panel 9 of FIG. 2 is obtained.

  In S4, the transparent cover 7 of FIG. 2 is manufactured or prepared. When a touch panel layer is connected instead of the transparent cover 7, the touch panel layer is manufactured or prepared.

  In S5, the photocurable adhesive 8 is manufactured or prepared. Details are shown in FIG. In addition, you may produce this adhesive agent 8 by mixing two or more types of adhesive agents, a polymerization initiator, etc. by S5.

  In S10, using the LCD panel 9 of S3 (with the polarizing plates 4 and 5), the transparent cover 7 of S4, and the photocurable adhesive 8 of S5, the polarizing plate of the LCD panel 9 as shown in FIG. The surface f1 of 5 and the surface f4 of the transparent cover 7 are bonded and bonded together with a photocurable adhesive 8. The process of S10 has, for example, the following first process of S11, second process of S12, and third process of S13.

  As the first step of S11, the photocurable adhesive 8 is applied to the inner surface when the LCD panel 9 and the transparent cover 7 are arranged to face each other. In this example, it has the process of apply | coating the adhesive agent 8 to the surface f4 (entire surface) of the transparent cover 7. FIG. As a coating method, a dispenser, slot die coating, slit coating, screen printing, or the like is used. In this example, the adhesive 8 is applied in a uniform layer form on the surface f4 of the transparent cover 7 with a thickness of, for example, 200 μm using a slit coat method. Note that S11 may be replaced with a step of applying the adhesive 8 to the surface f1 of the LCD panel 9.

  As the second step of S12, the surface f1 of the polarizing plate 5 of the LCD panel 9 and the application surface (f2) of the adhesive 8 of the transparent cover 7 of S11 are inward in a vacuum (that is, in the vacuum apparatus). Opposing each other at a fixed distance. At a predetermined degree of vacuum, they are gradually brought close to each other in the Z direction and are superposed (laminated) so that both surfaces (f1, f2) are in contact with each other. At this point, the adhesive 8 is in an uncured state. The laminated state is maintained for a certain period of time, and then the retained state is released and the atmosphere is released. In addition, there is an effect to prevent and eliminate bubbles by opening to the atmosphere. The LCD panel 9 in a state where the transparent cover 7 is stacked and laminated is taken out.

As the third step of S13, the front side of the transparent cover 7 with respect to the LCD panel 9 in which the transparent cover 7 of S12 is overlaid and stacked using the above-described irradiation device 300 (light source: high-pressure mercury ultraviolet lamp). The adhesive 8 is photocured by irradiating light including UV from the Z direction. The adhesive 8 is completely cured (adhered) by irradiating a predetermined amount of light (for example, 3000 mJ / cm ² ). Irradiation is stopped under the condition of the light quantity. Thus, the LCD 10 including the transparent cover 7 is obtained.

[Light source characteristics]
FIG. 7 shows an outline of a spectral distribution (characteristics of irradiation light including UV) in an example of a light source (high-pressure mercury ultraviolet lamp) of the irradiation apparatus 300 in the present embodiment. The light source (high pressure mercury ultraviolet lamp) of the irradiation apparatus 300 has a main output (spectral component) at a wavelength of 365 nm or more. For example, the main wavelength is 365 nm (w1), and the subwavelengths are 405 nm (w2) and 435 nm (w3).

  Corresponding to the characteristics of the light source, the photocurable adhesive 8 is mainly blended with a material having a high sensitivity in the vicinity of 365 nm (w1), for example, a polymerization initiator having a high ratio of absorbance at a wavelength of 365 nm. It is basically preferable to use

[Photo-curing adhesive]
FIG. 5 shows the composition, characteristics, and the like of the photocurable adhesive 8 which is an adhesive used in the first embodiment (described above S5). As shown in FIG. 5A, the photocurable adhesive 8 includes a polymerization initiator 81, a monomer 82 such as an acrylate monomer, an oligomer 83 such as an acrylate oligomer, and a polymer 84 as main compositions. The absorbance characteristics of the photocurable adhesive 8 are mainly determined by the characteristics of the polymerization initiator 81. The polymerization initiator 81 reacts (absorbs) with light containing UV, and initiates and accelerates the polymerization of the monomer 82 and the oligomer 83. The polymer 84 is included for the purpose of obtaining an appropriate viscosity when the adhesive 8 is applied / coated.

  FIG. 5B shows the absorbance characteristics of the polymerization initiator 81 (the ratio of absorbance at each absorbance wavelength). w1: 365 nm as the first absorption wavelength, w2: 405 nm as the second absorption wavelength, and w3: 435 nm as the third absorption wavelength. These are selected corresponding to the wavelength characteristics of the light source in FIG. FIG. 6 shows the relationship between the wavelengths and the like.

  Conventionally, a general photocurable adhesive increases the photocurability at 365 nm (w1), which is the dominant wavelength of the light source. For example, when the absorbance at 365 nm (w1) is 1, the absorbance is 405 nm (w2) or more. In many cases, a polymerization initiator is selected such that is about 0 to 0.1. That is, as a characteristic of the polymerization initiator of the conventional example, w1: w2 = 1: (0 to 0.1).

  On the other hand, the photo-curing adhesive 8 of the present embodiment has a non-UV (visible light) region or UV and visible as well as photo-curing property at a main wavelength of 365 nm (w1) of a light source that is a UV (about 400 nm or less) region. By increasing the photocurability at a wavelength of 405 nm (w2) in the vicinity of the light boundary, the irradiation time of UV (w1) to the polarizing plate 5 is suppressed. For this reason, the polymerization initiator 81 contained in the present photocurable adhesive 8 is configured to satisfy the following condition A and the like.

  As Condition A, the ratio (ratio) of absorbance for each wavelength is w1: w2 = 1: (0.25 to 0.5), where the absorbance at 365 nm (w1) is 1. The absorbance of w2 is set to the above (0.25 to 0.5) as a value larger than the conventional example (0 to 0.1). That is, with respect to the conventional example (w1: w2 = 1: (0 to 0.1)), in condition A, the degree of absorption of UV w1 (365 nm) is slightly suppressed, and the boundary with non-UV or visible light ( This is a configuration in which the degree of light absorption at a wavelength of w2 (405 nm) or more, which is a wavelength at which the PVA layer 52 of the polarizing plate 5 hardly absorbs, is further increased.

  As in the condition A, an adhesive 8 containing a polymerization initiator 81 having an absorbance at 405 nm (w2) larger than that of the conventional one is used. As a result, the irradiation time required for curing (adhesion) of the adhesive 8 with irradiation light including UV is shortened (the process of S13 can be completed quickly). Thereby, the influence (damage by shrinkage) to the polarizing plate 5 by irradiation light can be prevented and suppressed, and display quality is ensured.

  Note that w1 = 365 nm is selected in accordance with the dominant wavelength of the light source, as shown in FIG. Note that w2 = 405 nm corresponds to the sub wavelength of the light source and has a wavelength higher than UV (or the upper limit wavelength of the boundary region (eg, 360 to 405 nm)) that affects the polarizing plate 5 (shrinkage due to light absorption). Correspondingly selected. Note that w3 = 435 nm is selected corresponding to the sub-wavelength of the light source above w2.

  The lower limit value 0.25 of the absorbance range of w2 in the condition A is selected as a value sufficiently larger than the conventional value (0 to 0.1). The upper limit value 0.5 of the absorbance range of w2 in the above condition A is selected in accordance with the upper limit value in what can be manufactured / available as the present photocurable adhesive (polymerization initiator).

  As Example a that satisfies the condition A, for example, the absorbance ratio of the polymerization initiator 81 is w1: w2 = 1: 0.25. As another example b, w1: w2 = 1: 0.3. In another example c, w1: w2 = 1: 0.4. In another example d, w1: w2 = 1: 0.5. In any of the examples, the effect of ensuring the display quality was obtained. In particular, when the display device 10 was manufactured by selecting w1: w2 = 1: 0.5 and the display quality was evaluated, the display quality was not deteriorated, and good results were confirmed.

  Next, the condition B is as follows. As the polymerization initiator 81 having a larger w2 absorbance ratio as in the condition A is used, a higher effect (shortening) is obtained. However, many of the polymerization initiators having a large absorbance at a wavelength of w2 (405 nm) or longer, which is non-UV (visible light), have a light yellow color. Thereby, there exists a demerit which the transparency in a photocurable adhesive agent and the thing containing it falls. In the case of the above polymerization initiator, since it reacts in the visible light region, the curing of the adhesive is remarkably accelerated even under illumination such as a general fluorescent lamp. For this reason, during the process of bonding the transparent cover 7 and the LCD panel 9 at the time of manufacturing and during the work, the adhesive is immediately cured, which makes manufacturing difficult. For example, when an abnormality such as contamination of foreign matter occurs in the above-described stacked modules, it is difficult to peel off and regenerate.

  For the above reason, as the condition B (assuming the condition A), the absorbance ratio of the polymerization initiator 81 is reduced to the absorbance ratio of the wavelength in the visible light region. In particular, the ratio of absorbance at a wavelength of w3 (435 nm) or more is lowered. In particular, it is desirable to use a material that hardly absorbs light at 435 nm (w3) or more. The condition B is, for example, w1: w3 = 1: (0 to 0.1). w3 = 435 nm is selected corresponding to the wavelength 435 nm (FIG. 7) that appears as the sub wavelength of the light source. As a result, the absorption of the illumination light at a wavelength in the visible light region (particularly w3) is suppressed, and the transparency of the adhesive 8 after curing is increased.

For example, the following (both manufactured by BASF Japan Ltd.) can be used as the polymerization initiator 81 that exhibits characteristics satisfying the above conditions A and B contained in the photocurable adhesive 8:
2-Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (trade name: Irgacure 369),
2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone (trade name: Irgacure 379),
Bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide (trade name: Irgacure 1700),
A polymerization initiator (trade name: Irgacure 1800) in which bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and 1-hydroxycyclohexyl phenyl ketone were mixed at a ratio of 1: 3.
A polymerization initiator (trade name: Irgacure 1850) in which bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and 1-hydroxycyclohexyl phenyl ketone are mixed at a ratio of 1: 1.
A polymerization initiator (trade name: Trade name: 2-hydroxy-2-methyl-1-phenyl-propan-1-one and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide mixed 1: 1. Darocur 4265).

  As described above, the photocurable adhesive 8 manufactured / prepared in S5 may be prepared with one polymerization initiator, or may be prepared by mixing two or more kinds of polymerization initiators.

  Further, as the acrylate monomer 82 and the acrylate oligomer 83 contained in the photocurable adhesive 8, it is preferable to select an acrylate monomer 82 and an acrylate oligomer 83 that are easily accelerated and initiated by the polymerization initiator 81.

  The refractive index of the photocurable adhesive 8 (after curing) is desirably adjusted so that the refractive index difference from the transparent cover 7 is 0.03 or less in order to keep the display quality high. More preferably, the refractive index difference is 0.02 or less.

  Under the above conditions, a small error of ± a is allowed for w1 = 365 nm, w2 = 405 nm, and w3 = 435 nm. The wavelengths w1, w2, and w3 are selected in accordance with the characteristics of the light source (high pressure mercury ultraviolet lamp) (FIG. 7). Then, the values of the conditions w1, w2, and w3 may be adjusted.

[Relationship between wavelengths]
FIG. 6 shows the relationship between wavelengths in the visible light-UV region and the like in the present embodiment for understanding and supplementation. The horizontal axis is the wavelength of light [nm]. The visible light region is about 400-800 nm, and the UV (particularly near ultraviolet) region is about 200-400 nm. The boundary region is, for example, 365 nm to 405 nm.

  The UV region having a wavelength of about 400 nm or less gives an influence (shrinkage due to light absorption) on the PVA layer 52 of the polarizing plate 5. Correspondingly, the TAC layer (51, 53) has a property of protecting a wavelength of about 400 nm or less.

  The aforementioned w1 = wavelength 365 nm is the main wavelength of the light source (FIG. 7), and is selected as the main absorption wavelength of the adhesive 8 (polymerization initiator 81) correspondingly. The aforementioned w2 = wavelength 405 nm is a sub-wavelength of the light source (FIG. 7), is an upper limit value of the boundary region between UV and visible light, and is a wavelength that hardly affects the PVA layer 52 of the polarizing plate 5. Corresponding to this, the secondary absorption wavelength of the adhesive 8 (polymerization initiator 81) is selected.

[Absorbance of polarizing plate]
FIG. 8 shows a graph in which the absorbance at each wavelength in the above-mentioned conventional polarizing plate for LCD is measured. The absorbance here is a value for the entire polarizing plate. As shown in the figure, it can be seen that the polarizing plate has a high degree of absorption of light having a wavelength of around 400 nm (line a) or less.

The light absorbency is a dimensionless amount that represents the degree to which the intensity decreases when light passes through an object, and is a negative value obtained by taking the common logarithm of transmittance. Absorbance at wavelength λ A _λ = −log (I / I ₀ ), I: transmitted light intensity, I ₀ : incident light intensity.

[Effects]
As a comparative example for the first embodiment (adhesive 8), a similar LCD module was manufactured using a commercially available UV curable adhesive SVR1100 (Sony Chemical & Information Device Co.). That is, the LCD panel and the transparent cover similar to those of the first embodiment were cured by irradiating light including ultraviolet rays from the same light source with the UV curable adhesive SVR1100 overlapped. In this case, an integrated light amount of 5000 mJ / cm ² was required as the irradiation light amount for curing (complete adhesion) of the adhesive SVR1100. On the other hand, in this Embodiment 1, hardening (adhesion) was able to be achieved with the integrated light quantity of 3000 mJ / cm < ² > using the photocurable adhesive 8. FIG. Thereby, with respect to the comparative example, the time during which the polarizing plate 5 of the LCD panel 9 was exposed to UV light of about 400 nm or less including a wavelength of 365 nm could be shortened. By shortening the time, damage due to shrinkage of the PVA layer 52 of the polarizing plate 5 was prevented / reduced, and display quality deterioration due to polarization axis misalignment or the like was not substantially observed. That is, display quality can be ensured when the LCD 10 is manufactured.

<Embodiment 2>
Next, Embodiment 2 will be described with reference to FIG. The display device 10 and the manufacturing method thereof according to the second embodiment are different in the content of the third step S13 in the manufacturing method (FIG. 4) of the display device 10 according to the first embodiment. In the third step of S13 in the second embodiment, light having a wavelength of about 400 nm or less, which is the absorption wavelength of the polarizing plate 5 of the LCD panel 9, is blocked as a configuration of irradiation of light including ultraviolet rays from the irradiation device 300 (light source). Filter (UV blocking filter) 901 is used. The filter 901 is installed between the light source and the target LCD (10). The light including the UV from the light source is irradiated to the LCD (10) in the above-described stacked state of S12 through the filter 901. Accordingly, the adhesive 8 is irradiated with irradiation light having a wavelength of 405 nm (w2) or more to be cured. The light irradiation is performed until the integrated light amount reaches 5000 mJ / cm ² . By blocking UV of about 400 nm or less (including w1 = 365 nm) by the filter 901, the irradiation time (integrated light amount) is required for curing the adhesive 8, but the contraction damage due to the absorption of the polarizing plate 5 is prevented / suppressed. With regard to, higher effects can be obtained.

  FIG. 9 schematically shows an example of the light irradiation method in the third step of S13. The UV irradiation apparatus 300 has a configuration in which a filter 901 is installed between the light source and the target LCD (10). The LCD panel (10) in the stacked state of S12 is fixed on the stage or the transporting machine 900, transported in the X and Y directions, and downward from the light source of the UV irradiation device 300 on the upper side in the Z direction via the filter 901. Then, light including UV is irradiated. As a result, light having a wavelength of 400 nm or less blocked by the filter 901 is applied to the adhesive 8 of the target LCD (10) to be cured. As another form, the LCD panel (10) side may be fixed and the light source side may be moved.

[Measurement of degree of curing of adhesive]
As a supplement to the above-described embodiment, the degree of curing of the photo-curable adhesive 8 is a cured state, that is, a state where the adhesive 8 is in a cured state, that is, a state where the elastic modulus has increased 100 times or more. (The integrated light quantity at that time is the above-mentioned value). The elastic modulus was measured with a dynamic viscoelasticity measuring device (RS6000, HAAKE) while changing the integrated light quantity by irradiating ultraviolet rays.

<Effects>
As described above, according to each embodiment, in the manufacturing process in which the transparent cover 7 and the LCD panel 9 are bonded to each other with the adhesive 8, the wavelength absorbance ratio is 365 nm (w1): 405 nm (w2) = 1. : A photocurable adhesive 8 containing a polymerization initiator 81 of (0.25 to 0.5) is used. Thereby, the shrinkage | damage damage by the ultraviolet-ray of the polarizing plate 5 is suppressed, and the display quality of the display apparatus (LCD) 10 is securable. In the present embodiment, effects such as suppressing the influence on the polarizing plate 5 are realized by suitably designing the balance in the ratio of absorbance of each wavelength (w1, w2, w3) in the adhesive 8. .

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the present invention can be applied not only to the LCD panel 9 of the above embodiment but also to other display panels, for example, an organic EL display device using an organic EL panel. Further, the present invention is not limited to the polarizing plate, and can be similarly applied to a functional layer having a property of being deteriorated by UV. For example, the present invention can also be applied to an organic protective film such as a PET film used when a touch sensor layer or the like is attached to a panel.

  DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate (TFT array board | substrate), 2 ... 2nd board | substrate (color filter board | substrate), 3 ... Sealing material, 4, 5 ... Polarizing plate, 6 ... Liquid crystal layer, 7 ... Transparent cover, 8 ... Adhesive (Photo-curing adhesive), 9 ... liquid crystal display panel (LCD panel), 10 ... display device (LCD), 81 ... polymerization initiator, 82 ... monomer, 83 ... oligomer, 84 ... polymer.

Claims (11)

A display device in which a display panel and a transparent cover are bonded together using an adhesive,
The adhesive is a photocurable adhesive comprising a polymerization initiator,
When the first wavelength in the irradiation light for photocuring of the adhesive is around 365 nm and the second wavelength is around 405 nm,
The said polymerization initiator is 1st wavelength: 2nd wavelength = 1: (0.25-0.5) as a ratio of the light absorbency for every wavelength, The display apparatus characterized by the above-mentioned. The display device according to claim 1,
When the third wavelength in the irradiation light for photocuring of the adhesive is around 435 nm,
The said polymerization initiator is 1st wavelength: 3rd wavelength = 1: (0-0.1) as a ratio of the light absorbency for every wavelength, The display apparatus characterized by the above-mentioned. The display device according to claim 1 or 2,
The display device, wherein the adhesive includes a monomer and an oligomer that are positively polymerized by the polymerization initiator. The display device according to claim 1,
The display device, wherein the transparent cover is mainly made of glass or organic glass. The display device according to claim 1,
The display device, wherein the transparent cover is a touch panel layer. The display device according to claim 1,
The display panel has a polarizing plate on the side where the transparent cover is bonded using the adhesive,
The display device, wherein the polarizing plate and the transparent cover are bonded together with the adhesive. The display device according to claim 6, wherein
The polarizing plate includes a polarizer layer that is affected by ultraviolet rays including the first wavelength, and a protective layer that protects the polarizer layer from ultraviolet rays including the first wavelength. apparatus. A method for manufacturing a display device comprising a display panel and a transparent cover bonded together using an adhesive,
In the step of bonding the display panel and the transparent cover using the adhesive,
A first step of applying the adhesive to the surface of the display panel or the surface of the transparent cover;
A second surface of the display panel or the transparent cover on which the adhesive is applied and the surface of the display panel or the transparent cover on which the adhesive is not applied are overlapped so as to face each other. Process,
And a third step of photocuring the adhesive by irradiating light for photocuring of the adhesive onto the superposed surface using an irradiation device including a light source. And
The adhesive is a photocurable adhesive comprising a polymerization initiator,
When the first wavelength in the irradiation light for photocuring of the adhesive is around 365 nm and the second wavelength is around 405 nm,
The said polymerization initiator is 1st wavelength: 2nd wavelength = 1: (0.25-0.5) as a ratio of the light absorbency for every wavelength, The manufacturing method of the display apparatus characterized by the above-mentioned. In the manufacturing method of the display device according to claim 8,
When the third wavelength in the irradiation light for photocuring of the adhesive is around 435 nm,
The method for manufacturing a display device, wherein the polymerization initiator has a first wavelength: third wavelength = 1: (0 to 0.1) as a ratio of absorbance for each wavelength. In the manufacturing method of the display device according to claim 8,
In the third step, as a characteristic of the light source, the first wavelength is a dominant wavelength, and the second wavelength is a sub-wavelength. In the manufacturing method of the display device according to claim 8,
In the third step, when irradiating light on the superimposed surface from the light source, a filter that blocks a wavelength of about 400 nm or less between the light source and the superimposed surface. A display device manufacturing method characterized by being arranged.

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