JP2013029750A - Decorative filter and filter for image display device - Google Patents

Abstract

An object of the present invention is to provide a good decorative filter at low cost.
A light transmitting substrate, a resin film, and an adhesive for adhering the resin film and the substrate are provided, and a maximum refractive index Nx is obtained in the surface direction of the resin film. When one direction and the other direction having the minimum refractive index Ny are set, and the refractive index in the thickness direction of the resin film is Nz, the value of (Nx−Nz) / (Ny−Nz) is 1 ≦ (Nx−Nz) / (Ny−Nz) ≦ 1.12, or 1.6 ≦ (Nx−Nz) / (Ny−Nz), and the thickness t of the resin film is 20 μm ≦ t ≦ 150 μm. The above-mentioned problem is solved by providing a decorative filter characterized by being.
[Selection] Figure 8

Description

  The present invention relates to a decorative filter and a filter for an image display device.

  In recent years, in an image display device such as a liquid crystal display, a display screen provided with a decorative filter on the front surface is increasing. The decorative filter has an antireflection function to make the display on the image display device easier to see, and improves the aesthetics of the image display device to give a high-class feeling, etc. Therefore, an image display device equipped with a decorative filter is an added value Will be expensive. For this reason, in the image display device, the importance of the decorative filter is high. As such a decorative filter, there exists a thing of the structure where the transparent film which consists of a resin material is affixed on the glass substrate, as patent document 1 and 2 show.

JP 2003-66226 A JP 2006-163151 A

  By the way, in an image display apparatus, cost reduction is one of the important elements. In other words, the use of a low-cost decorative filter makes it possible to reduce the overall price of the image display device, and thus a low-cost decorative filter having good functionality is desired.

  The present invention has been made in view of the above, and an object of the present invention is to provide a decorative filter and a filter for an image display device that are favorable at low cost.

  The present invention includes a substrate that transmits light, a resin film, and an adhesive for bonding the resin film and the substrate, and has a maximum refractive index Nx in the surface direction of the resin film. When one direction and the other direction having the minimum refractive index Ny are set, and the refractive index in the thickness direction of the resin film is Nz, the value of (Nx−Nz) / (Ny−Nz) is 1 ≦ (Nx−Nz) / (Ny−Nz) ≦ 1.12, or 1.6 ≦ (Nx−Nz) / (Ny−Nz), and the thickness t of the resin film is 20 μm ≦ t ≦ 150 μm. It is characterized by being.

  The present invention also includes a substrate that transmits light, a resin film, and an adhesive for bonding the resin film and the substrate, and has a maximum refractive index Nx in the surface direction of the resin film. When the refractive index in the thickness direction of the resin film is Nz, the value of (Nx−Nz) / (Ny−Nz) is 1 ≦ (Nx−Nz) / (Ny−Nz) ≦ 1.12, or 1.6 ≦ (Nx−Nz) / (Ny−Nz), and the thickness t of the resin film is 20 μm ≦ t ≦ 150 μm, and the refractive indexes Nx and Ny in the in-plane direction of the resin film are 1.6 <Nx and 1.6 <Ny, and the refractive index Nx in the film thickness direction of the resin film is Nx. <1.5.

  The present invention is characterized in that the resin film is formed of a material containing a polyethylene terephthalate resin.

  Further, the present invention is characterized in that the resin film has an antireflection film on a surface opposite to a surface bonded to the substrate.

  Further, the present invention is characterized in that an easy-adhesion layer is provided on the surface of the resin film to be bonded to the substrate so that the pressure-sensitive adhesive is easily attached.

  Further, the present invention is characterized in that the one direction and the other direction are substantially orthogonal to each other.

  In addition, the present invention includes the decorative filter described above, and is installed on the display surface side of the image display device.

  According to the present invention, the image display device is any one of a liquid crystal display, a PDP, and an EL display.

  According to the present invention, it is possible to provide a decorative filter and a filter for an image display device that are favorable at a low price.

Decorative filter structure diagram Cross-Nicol state evaluation device structure diagram Correlation diagram of tilt angle and retardation when rotated around the x-axis Correlation diagram of tilt angle and retardation when rotated about the y-axis Illustration of the cause of rainbow unevenness Correlation diagram between refractive index difference ΔN and angle θi Correlation diagram between refractive index Nz and angle θi Structure diagram of decorative filter and filter for image display device in the present embodiment

  Modes for carrying out the invention will be described below. In addition, about the same member etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 1, a decorative filter 200 for an image display device such as a liquid crystal has a structure in which an antireflection film 220 is attached to a glass substrate 210 with an adhesive 230. In the antireflection film 220, an easy-adhesion layer 223 is provided on one surface so that the adhesive 230 can be easily adhered, and an antireflection layer 222 is formed on the other surface. Such a decorative filter 200 is installed so that the glass substrate 210 is on the image display device side, and a person can pass through the decorative filter 200 from the surface on which the antireflection film 222 is formed to the image display device. Recognize the displayed image.

  As such a resin film 221, TAC (Triacetylcellulose) resin is mainly used. However, if a lower priced polyethylene terephthalate (PET) resin can be used, the decorative filter 200 can be manufactured at a low price. Thus, the price of the image display device can be further reduced.

  By the way, in the decorative filter 200 using the resin film 221 made of PET resin as described above, it has been confirmed that ring-shaped rainbow-colored interference fringes (hereinafter referred to as rainbow unevenness) occur, and such rainbow unevenness occurs. This will also affect aesthetics and visibility. In particular, when an interference fringe with a narrow center or interval between ring-shaped rainbow unevenness occurs, the rainbow unevenness is easily noticeable. Such rainbow unevenness does not occur when a TAC resin is used as the resin film 221, which is a major problem when a PET resin is used as the resin film 221 in the decorative filter 200.

  The inventors have studied the cause of the rainbow unevenness. As a result, the rainbow unevenness is caused by the material of the resin film 221 forming the decorative filter 200. It is especially easy to confirm when a member that reflects light such as a desk is installed in front, and it is easy to observe near a predetermined angle. It came. From these facts, it is inferred that rainbow unevenness is caused by the fact that light in a certain polarization state is incident on the resin film 221 and the polarization state of the light changes in the resin film 221, and specifically, It is guessed as follows. That is, when the light is incident on a member that reflects light such as a desk at an angle close to the Brewster angle, the reflected light has a polarization state close to a certain linearly polarized light and is incident on the resin film 221. The polarization state changes due to the phase difference in the PET resin forming the. Thereafter, light is reflected by the glass surface on the opposite side to which the resin film 221 is attached, and the polarization state of the reflected light is changed by the resin film 221, and light is emitted from the resin film 221. When reflected on the glass surface opposite to the surface on which the resin film 221 is attached, or when light is emitted from the resin film 221, the angle is close to the Brewster angle. The light emitted from the resin film 221 varies depending on the wavelength. Therefore, it is assumed that rainbow-colored interference fringes are generated.

  In addition, when the characteristics of the PET resin used as the resin film 221 is changed, the occurrence of rainbow unevenness is different, and it has been confirmed that there are cases where rainbow unevenness occurs remarkably and not. .

  This will be described based on the sample S1, the sample S2, the sample S3, and the sample S4 made of PET resins having different characteristics. Sample S1 is formed using a certain PET resin so as to have a thickness of 188 μm. The center of rainbow unevenness is confirmed, and interference fringes of rainbow unevenness are remarkably generated. The sample S2 is formed using the same PET resin as the sample S1 so as to have a thickness of 100 μm. The center of the rainbow unevenness is confirmed, but the interference fringes are lower than the sample S1. Sample S3 is formed using a PET resin different from sample S1 so that the thickness is 188 μm. The center of the rainbow unevenness is not confirmed, but the interference fringes of the rainbow unevenness are observed to the same extent as in sample 1. The The sample S4 is formed using the same PET resin as the sample S3 so as to have a thickness of 100 μm, and the generated rainbow unevenness is inconspicuous.

  First, in the evaluation apparatus for observing the so-called crossed Nicols state having the light source unit 11, the polarizer 12, and the analyzer 13, as shown in FIG. 2, the sample is tilted with respect to the samples S1 to S4. The generation of rainbow unevenness will be described. The polarizer 12 and the analyzer 13 are set in a so-called crossed Nicol state, the samples S1 to S4 are rotated between the polarizer 12 and the analyzer 13, and the sample is rotated to check the optical axes of the samples S1 to S4 by the extinction state. did. When the states of the samples S1 to S4 when the sample was tilted about the optical axis were observed, rainbow unevenness occurred only when the sample was rotated about one optical axis.

  The change in retardation will be described with the optical axis where the center of rainbow unevenness does not occur at the x-axis and the optical axis where the center of rainbow unevenness occurs as the y-axis. Retardation was measured by RETS-100 manufactured by Otsuka Electronics. The results are shown in FIGS. The wavelength used for the measurement is 550 nm. FIG. 3 shows a case where the samples S1 to S4 are inclined with the x axis as the central axis, and FIG. 4 shows a case where the samples S1 to S4 are inclined with the y axis as the central axis. is there.

  As shown in FIGS. 3 and 4, the sample S4 in which the rainbow unevenness is not confirmed so much has a lower retardation value than the samples S1, S2 and S3 as a whole. In addition, as shown in FIG. 4, when rotated around the y-axis, the samples S3 and S4 have an inclination angle θ of about 20 ° and a retardation of about 0 nm, whereas in the samples S1 and S2, The retardation is about 0 nm when the inclination angle θ is around 45 °. Further, in the samples S1 and S2 or the samples S3 and S4, the smaller the thickness, the lower the retardation value.

  From the above, it is considered that rainbow unevenness is caused by retardation, and it is presumed that generation of rainbow unevenness can be suppressed by lowering the retardation value.

  Next, generation of rainbow unevenness when the sample is tilted by the refractive index will be described. The refractive index was measured with a Metricon model 2010 prism coupler. The measurement used a He-Ne laser with a wavelength of 632.8 nm, the refractive index in the in-plane direction was TE mode, and the refractive index in the thickness direction was TM mode. As shown in Table 1, the resin films molded into a plate shape using PET resin have different refractive indexes in the three-dimensional direction. That is, the sample S1 and the sample S3 made of PET resin differ in the refractive index Nx in the x-axis direction, the refractive index Ny in the y-axis direction, and the refractive index Nz in the thickness direction (hereinafter z-axis). On the other hand, in the resin film molded into a plate shape using TAC resin, the refractive index Nx in the x-axis direction, the refractive index Ny in the y-axis direction, and the refractive index Nz in the z-axis direction are substantially equal. Note that the x-axis direction, the y-axis direction, and the z-axis direction are orthogonal to each other. When the refractive index ellipsoid in the samples S1 and S3 is assumed, the angle θt is an angle at which light propagates in a direction perpendicular to the plane in which the cross section becomes a circle, and as shown in FIG. An angle formed with the z axis in the plane is shown. The angle θi is an angle for allowing light to enter the samples S1 and S3 so that the light travels at an angle θt with respect to the z axis in the samples S1 and S3. The sample S2 is considered to be the same as the sample S1, and the sample S4 is considered to be the same as the sample S3.

The angle θt in Table 1 is calculated by using an ellipse equation from Nx, Ny, and Nz. The angle θi is expressed by the following equation (1) according to Snell's law. Since it has a relationship, it is calculated based on the equation shown in (1). Note that n ₀ is the refractive index of air and is 1.

n ₀ × sin θi = {(Nx + Ny) / 2} × sin θt (1)

表１に示されるように、虹ムラが顕著に発生する試料Ｓ１では、角度θｉは４２．１°であるのに対し、虹ムラがあまり確認されない試料Ｓ３では、角度θｉは１８．３°である。尚、試料Ｓ１〜Ｓ４は、面内方向における屈折率Ｎｘ、Ｎｙは、ともに、屈折率は１．６以上であり、厚さ方向における屈折率Ｎｚは、１．５以下である。即ち、１．６＜Ｎｘ、１．６＜Ｎｙであり、Ｎｚ＜１．５である。

As shown in Table 1, the angle θi is 42.1 ° in the sample S1 in which the rainbow unevenness is remarkably generated, whereas the angle θi is 18.3 ° in the sample S3 in which the rainbow unevenness is not much confirmed. is there. Samples S1 to S4 both have a refractive index Nx and Ny in the in-plane direction of 1.6 or more, and a refractive index Nz in the thickness direction of 1.5 or less. That is, 1.6 <Nx, 1.6 <Ny, and Nz <1.5.

  By the way, in the material used as the resin film 221, the transmittance and the reflectance may be different depending on the polarization direction of the incident light. In this case, the transmittance and the reflectance are different depending on the incident angle. The difference becomes remarkable. For example, when light is incident on a medium having a refractive index of 1.5, a range of 0 ° to 30 ° (meaning 0 ° or more and 30 ° or less) from a direction perpendicular to a surface formed by the medium. Then, the transmittance and the reflectance are the same value without depending on the polarization direction so much, but in the range of 30 ° to 80 ° (which means more than 30 ° and less than 80 °), the polarization direction. Depending on the transmission, the transmittance and the reflectance are greatly different. That is, the light incident on the resin film 221 is considered to be light whose polarization state is biased due to some reason such as reflection of the desk, and the light is transmitted by being incident on the resin film 221 at a predetermined angle. Polarization separation occurs in light and reflected light. As a result, it is assumed that rainbow unevenness similar to that confirmed by the evaluation apparatus of FIG. 2 occurs. The Brewster angle in a medium with a refractive index of 1.5 is about 56 °, and the Brewster angle in a medium with a refractive index of 1.65 is about 59 °. In particular, the rainbow unevenness is remarkable around this angle. Observed.

  In the sample S1 in which the center of the rainbow unevenness is remarkably confirmed, the angle θi is 42.1 °, and the transmittance and the reflectance are greatly different depending on the polarization direction. The sample S3 in which the center of unevenness is not confirmed so much has an angle θi of 18.3 °, and is in the range of 0 ° to 30 ° where the transmittance and the reflectance do not depend much on the polarization state. Therefore, when the angle θi is in the range of 30 ° <θi <80 °, the central portion of the rainbow unevenness is likely to occur, and in the range of 0 ° ≦ θi ≦ 30 ° or 80 ° ≦ θi ≦ 90 ° The central part is presumed to be difficult to occur. Therefore, the angle θi is preferably in the range of 0 ° ≦ θi ≦ 30 ° or 80 ° ≦ θi ≦ 90 °.

  By the way, the angle θi depends on the relationship between Nx, Ny, and Nz. FIG. 6 shows the relationship between the angle θi and the refractive index difference ΔN when (Nx + Ny) /2=1.66 and ΔN = Nx−Ny. Based on FIG. 6, depending on Nz, ΔN for setting 0 ° ≦ θi ≦ 30 ° and ΔN for setting 80 ° ≦ θi vary depending on the value of Nz. On the other hand, as shown in FIG. 7, the angle θi is correlated with (Nx−Nz) / (Ny−Nz), and in order to satisfy 0 ° ≦ θi ≦ 30 °, 1 ≦ (Nx−Nz) /(Ny−Nz)≦1.12. Further, in order to satisfy 80 ° ≦ θi, it is necessary to satisfy 1.6 ≦ (Nx−Nz) / (Ny−Nz). The values of (Nx−Nz) / (Ny−Nz) of sample S1 and sample S3 were 1.22 and 1.04, respectively.

  Furthermore, as described above, since the interval between the stripes of the rainbow unevenness also depends on the retardation value, it is considered effective to reduce the thickness in order to make the rainbow unevenness inconspicuous.

  Table 2 shows the occurrence of rainbow unevenness when the samples S1 to S11 are tilted by 45 ° about the y-axis direction and tilted by 60 ° in the apparatus shown in FIG. Sample S5, Sample S6, Sample S7, and Sample S8 are formed using the same PET resin as Sample S1 so as to have thicknesses of 150 μm, 125 μm, 50 μm, and 38 μm, respectively. Sample S9, Sample S10, Sample S11 Are formed using the same PET resin as sample S3 so as to have thicknesses of 150 μm, 125 μm, and 50 μm, respectively. When the center of the rainbow unevenness is confirmed, X is indicated, and when the center is not determined is indicated as ◯. When the sample is tilted 5 ° back and forth, the number of rainbow uneven interference is counted. Is x. In all the evaluations, in all the judgments, “good” means “good”, “good” means “good”, and any “good” means “poor”.

表２より、加飾フィルタを形成するための樹脂フィルムの厚さｔは、１５０μｍ以下であることが好ましく、更には、１２５μｍ以下であることが好ましい。尚、樹脂フィルムとしての形態を維持するためには、厚さは２０μｍ以上であることが好ましい。以上より、樹脂フィルムの厚さｔは、２０μｍ≦ｔ≦１５０μｍであることが好ましく、更には、３０μｍ≦ｔ≦１２５μｍであることが好ましい。

From Table 2, the thickness t of the resin film for forming the decorative filter is preferably 150 μm or less, and more preferably 125 μm or less. In addition, in order to maintain the form as a resin film, it is preferable that thickness is 20 micrometers or more. From the above, the thickness t of the resin film is preferably 20 μm ≦ t ≦ 150 μm, and more preferably 30 μm ≦ t ≦ 125 μm.

  Based on these, the decorative filter and the image display device filter in the present embodiment will be described. As shown in FIG. 8, the decorative filter 100 in the present embodiment has a structure in which an antireflection film 120 is attached to a glass substrate 110 with an adhesive 130. In the antireflection film 120, an easy adhesion layer 123 is provided on one surface in contact with the pressure-sensitive adhesive 130, and an antireflection layer 122 is formed on the other surface.

  In the present embodiment, the resin film 121 is formed of PET resin, and the thickness t of the resin film 121 is formed so as to satisfy 20 μm ≦ t ≦ 150 μm, more preferably 30 μm ≦ t ≦ 125 μm. For example, it is formed with a thickness of about 100 μm. Further, in the in-plane direction of the resin film 121, the refractive index in the direction in which the refractive index is maximum (this direction is the x-axis direction) is Nx, and the refractive index in the y-axis direction, which is a direction substantially orthogonal to the x-axis. Is Ny and the refractive index in the z-axis direction that is the thickness direction of the resin film 121 is Nz, the value of (Nx−Nz) / (Ny−Nz) is 1 ≦ (Nx−Nz) / (Ny -Nz) ≦ 1.12, or a resin material satisfying 1.6 ≦ (Nx−Nz) / (Ny−Nz). When the PET resin is formed in a film shape, the direction in which the refractive index is maximum and the direction in which the refractive index is minimum are substantially orthogonal in the in-plane direction of the film. Therefore, in the above case, the y-axis direction is the direction in which the refractive index is minimum.

  The glass substrate 110 is made of a glass material having a refractive index of about 1.52 and a thickness of about 2 mm. The antireflection layer 122 includes a silica-based material or fluoride, and is formed to have a predetermined film thickness using a low refractive index material having a lower refractive index than that of the resin film 121. The easy adhesion layer 123 has a refractive index of 1.5 to 1.6 and a thickness of 0.05 μm to 0.1 μm. The pressure-sensitive adhesive 130 has a refractive index of about 1.48 and a thickness of about 25 μm.

  Further, in the decorative filter and the image display device filter in the present embodiment, glass is used as the glass substrate 110, but it may be formed of a resin material or the like that transmits visible light instead of glass. .

  The decorative filter 100 is installed so that the side on which the image display device is located is the glass substrate 110 side, and is used as a filter for the image display device. Examples of such an image display device include a liquid crystal display, a PDP (Plasma Display Panel), an EL display including an organic EL (Electro Luminescence) display, and the like.

  In addition, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

DESCRIPTION OF SYMBOLS 100 Decorative filter 110 Glass substrate 120 Antireflection film 121 Resin film 122 Antireflection layer 123 Easy adhesion layer 130 Adhesive 140 Image display apparatus

Claims (8)

A substrate that transmits light;
A resin film;
A pressure-sensitive adhesive for bonding the resin film and the substrate;
In the surface direction of the resin film, one direction having the maximum refractive index Nx and the other direction having the minimum refractive index Ny are set, and the refractive index in the thickness direction of the resin film is Nz. In this case, the value of (Nx−Nz) / (Ny−Nz) is 1 ≦ (Nx−Nz) / (Ny−Nz) ≦ 1.12, or 1.6 ≦ (Nx−Nz) / (Ny−Nz). ) And
A thickness t of the resin film is 20 μm ≦ t ≦ 150 μm. A substrate that transmits light;
A resin film;
A pressure-sensitive adhesive for bonding the resin film and the substrate;
In the surface direction of the resin film, one direction having the maximum refractive index Nx and the other direction having the minimum refractive index Ny are set, and the refractive index in the thickness direction of the resin film is Nz. In this case, the value of (Nx−Nz) / (Ny−Nz) is 1 ≦ (Nx−Nz) / (Ny−Nz) ≦ 1.12, or 1.6 ≦ (Nx−Nz) / (Ny−Nz). ) And
The thickness t of the resin film is 20 μm ≦ t ≦ 150 μm,
Refractive indexes Nx and Ny in the in-plane direction of the resin film are 1.6 <Nx and 1.6 <Ny,
Refractive index Nx in the film thickness direction of the resin film is Nx <1.5.   The decorative filter according to claim 1 or 2, wherein the resin film is formed of a material containing polyethylene terephthalate resin.   The decorative filter according to any one of claims 1 to 3, wherein the resin film has an antireflection film on a surface opposite to a surface to be bonded to the substrate.   5. The additive according to claim 1, wherein an easy-adhesion layer is provided on a surface of the resin film to be bonded to the substrate so that the pressure-sensitive adhesive is easily attached. Decorative filter.   The decorative filter according to any one of claims 1 to 5, wherein the one direction and the other direction are substantially orthogonal to each other. Including the decorative filter according to claim 1,
A filter for an image display device, which is installed on the display surface side of the image display device.   The image display device filter according to claim 7, wherein the image display device is one of a liquid crystal display, a PDP, and an EL display.

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