JP2005049846A - Laminated sheet and method for designing the sheet and back projection type screen and method for producing the screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back projection type screen in which degradation in image or image quality caused by a temperature change is prevented and a method for producing the screen and a laminated sheet and a method for designing the laminated sheet. <P>SOLUTION: The back projection type screen is one that includes the laminated sheet having n number of layers (n represents a natural number not smaller than 3). A difference between the linear expansion coefficient of the layer having the highest linear expansion coefficient of the laminated sheet and that of the layer having the lowest linear expansion coefficient of the laminated sheet is not less than 5%. Further, a difference between the elastic modulus of the layer having the maximum elastic modulus of the laminated sheet and that of the layer having the minimum elastic modulus is 10% or more. The calculated value ε(1/mm°C) of a rate at which the curvature of the sheet changes relative to temperature is -7.0×10<SP>-6</SP>≤ε≤+7.0×10<SP>-6</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminated sheet and a design method thereof, and a rear projection type screen and a manufacturing method thereof.

  Conventionally, as a rear projection type screen, a screen composed of a plurality of sheet-like members such as a lenticular lens sheet, a Fresnel lens sheet, and a front plate has been mainly used. In the screen market, while the screen size is increasing, there is a tendency to reduce the thickness for the purpose of weight reduction, cost reduction, and pitch refinement. Further, in order to increase the functionality of the rear projection type screen, the number of Fresnel lenses (hereinafter referred to as “Fresnel”), lenticular lenses (hereinafter referred to as “wrench”), and front plates that are integrated into a multilayer structure is increasing. For example, a two-layer wrench, a two-layer Fresnel, a film-attached front plate, etc., and a thin screen having a multilayer structure is mainly used at present. Furthermore, a screen having a configuration in which color shift and contrast are improved by bonding a front plate and a wrench with an external light absorption layer protrusion (black stripe, BS) has been proposed (for example, Patent Document 1). In addition, wrench for liquid crystal display and DMD (Digital Micromirror device) is mainly a very thin film wrench, and it is almost impossible to stand alone. For example, a liquid crystal display film wrench and a front plate bonded with a wrench exit surface have been proposed. Further, there is a structure in which an antireflection film is provided on the exit surface side of the front plate. Furthermore, there is one in which the difference in the linear expansion coefficient of each layer is increased so that a sheet having a multilayer structure of two or more layers is warped in advance (for example, Patent Document 2). Thus, various types of rear projection screens having a multilayer structure are used.

  However, the following problems have occurred in the rear projection type screen in which such films and the like are bonded and integrated. When films of different materials, lens sheets, front plates, etc. are used, the thermal expansion occurs due to temperature changes during use because the linear expansion coefficient differs depending on the respective materials. The warp due to the thermal stress deforms the lens and fluctuates the focal position of the screen, and the film may cause separation. As a result, there has been a problem that the image and image quality of the rear projection type screen deteriorate. Even if different materials are used alone, the focal position varies to some extent, but the focal position varies greatly by progressing with multiple layers and integration, and the image and image quality deteriorate. Became a more serious problem.

  In order to prevent warping deformation due to temperature changes in bonded products or multilayer products of different materials, it is necessary to adjust the thickness ratio of each layer and make other layers as thin as possible with respect to the layer that is the center of rigidity. Conceivable. For example, warping caused by thermal stress can be reduced by making the thickness of one material extremely thick compared to the thickness of the other layers. Alternatively, it is conceivable to adjust the elastic modulus ratio of each layer and arrange a soft layer with a negligible deformation force on the rigid central layer. Furthermore, it is conceivable to make the linear expansion coefficients of the respective layers substantially equal. It is possible to prevent warping due to thermal expansion by making the configuration of the laminate symmetrical in the thickness direction, but in that case, the design becomes more restrictive, such as another material can not be used on the front and back of the sheet . However, these methods have a problem in that the constraint conditions are severe from the viewpoint of thickness reduction and material selection, and the degree of freedom is very narrow, and the composition, material, and thickness cannot be freely changed. That is, the change in elastic modulus is accompanied by a change in composition and material, and there are cases where the optical characteristics change or the total plate thickness is limited due to the demand for thinning.

JP-A-7-248537 JP 2001-133886 A

  As described above, the conventional rear projection screen has a problem that the image and the image quality are deteriorated due to the temperature change.

  The present invention has been made to solve such problems, and provides a rear projection screen capable of preventing image and image quality deterioration due to temperature change, a manufacturing method thereof, a laminated film, and a design method thereof. For the purpose.

（ここで前記積層シートの貼り合せ後の曲率（１／ｍｍ）をθ、前記積層シートの第ｉ層目（ｉ＝１，２・・・ｎ）の板厚（ｍｍ）をｔ_ｉ、前記積層シートの片側の面を０とし、片側の面から反対側の面への厚み方向の距離（ｍｍ）をｙ、前記積層シートのｙにおける弾性率をＥ（ｙ）、前記積層シートのｙ＝０（ｍｍ）における貼り合せ後の伸び（無次元）をｅ0、前記積層シートのｙにおける材質の貼り合せ前の自由伸び（無次元）をe(y)、前記積層シートのｙにおける材質の線膨張率（１／℃）をα(y)、とする。）これにより、温度変化による反りを低減することができる。 The laminated sheet according to the present invention is a laminated sheet having a multilayer structure asymmetric in the thickness direction of n layers (n is a natural number of 3 or more), and the linear expansion of the layer having the maximum linear expansion coefficient of the laminated sheet The layer having the smallest coefficient of linear expansion with respect to the modulus has a coefficient of linear expansion of 95% or less, the modulus of elasticity of each layer of the laminated sheet is within 10,000 MPa, and the layer having the maximum modulus of elasticity has the smallest elasticity. The laminated sheet has an elastic modulus of 90% or less, and the thickness of the thickest layer of the laminated sheet is within 200 times the thickness of the thinnest layer, and is calculated by the simultaneous equations of Equation 3 below A laminated sheet having a calculated value ε (1 / mm ° C.) of a curvature change rate with respect to the temperature of −7.0 × 10 ⁻⁶ ≦ ε ≦ + 7.0 × 10 ⁻⁶ .

(Here, the curvature (1 / mm) after lamination of the laminated sheet is θ, the plate thickness (mm) of the i-th layer (i = 1, 2,... N) of the laminated sheet is t _i , The surface on one side of the laminated sheet is 0, the distance (mm) in the thickness direction from the surface on one side to the opposite side is y, the elastic modulus at y of the laminated sheet is E (y), and y = The elongation (non-dimensional) after bonding at 0 (mm) is e0, the free elongation (non-dimensional) before bonding of the material at y of the laminated sheet is e (y), and the material line at y of the laminated sheet (Expansion coefficient (1 / ° C.) is assumed to be α (y).) Thereby, warpage due to temperature change can be reduced.

  The above laminated sheet is preferably used for a rear projection type screen. Thereby, it is possible to prevent the deterioration of the image and the image quality due to the temperature change.

前記連立方程式より求められた曲率θに基づいて曲率変化率εを各層の弾性率Ｅ_ｉ、板厚ｔ_ｉ及び線膨張率α_ｉの関数として算出するステップと、前記曲率変化率εを−７．０×１０^−６≦ε≦＋７．０×１０^−６とするように前記弾性率Ｅｉ、前記板厚ｔ_ｉ及び前記線膨張率α_ｉを決定するステップ、とを有するものである。これにより、積層シートの温度変化による反りを低減することができる。 A method for designing a laminated sheet according to the present invention is a design method for designing the material and thickness of each layer of a laminated sheet having a multilayer body that is asymmetric in the thickness direction of n layers (n is a natural number of 3 or more). The linear expansion coefficient of the layer having the minimum linear expansion coefficient relative to the linear expansion coefficient of the layer having the maximum linear expansion coefficient of the laminated sheet is 95% or less, and the elastic modulus of each layer of the laminated sheet is within 10,000 MPa. The elastic modulus of the layer having the minimum elastic modulus relative to the elastic modulus of the layer having the maximum elastic modulus is 90% or less, and the thickness of the thickest layer of the laminated sheet is within 200 times the thickness of the thinnest layer. Yes, the curvature (1 / mm) after the lamination of the laminated sheets is θ, the plate thickness (mm) of the i-th layer (i = 1, 2,... N) of the laminated sheets is t _i , and the laminated The surface on one side of the sheet is 0, and the surface on the opposite side from the surface on one side The thickness direction distance (mm) to y, the elastic modulus at y of the laminated sheet as E (y), the elongation (non-dimensional) after lamination at y = 0 (mm) of the laminated sheet as e0, E (y) is the free elongation (dimensionless) of the laminated sheet before bonding the material at y, the linear expansion coefficient (1 / ° C) of the material at y of the laminated sheet is α (y), and the temperature of the laminated sheet In the case of the curvature change rate ε with respect to the change, the step of eliminating e0 in the simultaneous equations shown below and solving for the curvature θ;

Calculating the curvature change rate ε as a function of the elastic modulus E _i , the plate thickness t _i and the linear expansion coefficient α _i of each layer based on the curvature θ obtained from the simultaneous equations _; and the curvature change rate ε is −7. Determining the elastic modulus Ei, the plate thickness t _i and the linear expansion coefficient α _i so as to satisfy 0.0 × 10 ⁻⁶ ≦ ε ≦ + 7.0 × 10 ⁻⁶ . Thereby, the curvature by the temperature change of a lamination sheet can be reduced.

  The manufacturing method of a rear projection type screen according to the present invention includes a step of producing a sheet designed by the above-described method of designing a rear projection type screen sheet, and a step of fixing the sheet to a frame. Thereby, it is possible to prevent the deterioration of the image and the image quality due to the temperature change.

  ADVANTAGE OF THE INVENTION According to this invention, the image by a temperature change, the rear projection type screen by which degradation of the image quality was suppressed, its manufacturing method, a lamination sheet, and its design method can be provided.

  FIG. 1 shows a configuration of a rear projection type screen according to the present embodiment. FIG. 1 is a perspective view of a rear projection screen. 1 is a lenticular lens sheet, 2 is a Fresnel lens sheet, 3 is a front plate, 11 is a lenticular lens, 12 is a condensing part, 13 is a non-condensing part, and 14 is an external light absorbing part. The rear projection type screen is composed of a Fresnel lens sheet 2, a lenticular lens sheet 1, and a front plate 3 in this order from the light incident surface.

  The Fresnel lens sheet 2 is generally composed of a sheet in which a Fresnel lens made of concentric and fine pitch lenses at equal intervals is provided on the light exit surface. The lenticular lens sheet 1 is composed of a translucent substrate, and a plurality of lenticular lenses 11 are formed on a surface on which image light is incident. Of the surfaces of the lenticular lens sheet 1 from which image light is emitted, it is common to form a condensing part 12 in the shape of a convex lens, on which light from the lenticular lens 11 formed on the incident side surface is condensed. The reason why the condensing part 12 is formed in a convex lens shape is to improve the diffusion performance of the image light in the horizontal direction.

  Further, in the lenticular lens sheet 1 used in combination with the three-tube CRT light source, it is necessary to form the light condensing part 12 in a convex lens shape particularly in order to correct the color misregistration of the three colors. The non-condensing part 13 (the part other than the condensing part 12) where the light from the lenticular lens 11 formed on the incident side surface does not condense is composed of a top part and a side face parallel to the lenticular lens sheet 1. It is convex. Then, an external light absorbing layer 14 made of black paint or the like is provided on the top of the convex portion and the portion near the top of the convex portion side surface (upper side surface) by means of roll coating, screen printing, transfer printing, etc. A shaped external light absorbing portion (BS portion) is formed. This reduces the amount of external light incident on the lenticular lens sheet 1 that is reflected by the exit surface of the lenticular lens sheet 1 and returns to the viewer side, thereby improving the image contrast.

  An example of the configuration of the front plate 3 is shown in FIG. FIG. 2 is a side view showing the configuration of the front plate 3. 4 is a PET film. In the present embodiment, an antistatic PET film 4 is bonded to the front surface (surface on the observer side) of the front plate 3. The front plate 3 is made of a methyl methacrylate / styrene monomer copolymer (hereinafter referred to as MS). The PET film 4 is made of polyethylene terephthalate (hereinafter referred to as PET). The front plate 3 and the PET film 4 can be bonded using a photocurable adhesive. A configuration in which the warpage of such a two-layer structure is reduced will be described. In the present specification, a sheet composed of two or more layers is referred to as a multilayer body.

First, the stress and bending moment generated in a multilayer of two or more layers (i layers) due to thermal stress are obtained. Here, a two-layer laminated sheet will be described as the simplest example. For the sake of explanation, it is assumed that a coordinate system as shown in FIG. 3 is taken, and sheets of the first layer (material 1) and the second layer (material 2) are provided in order in the Y-axis direction. F is the stress per unit width (N / mm) generated in the multilayer body by thermal expansion, M is the bending moment (Nmm / mm) per unit width generated in the multilayer body by thermal expansion, and θ is the laminated sheet one surface of the sheet thickness (mm), the y the laminated sheet of curvature after the bonding (1 / mm), the i-th layer of the laminated sheet _{t i (i = 1,2 ··· n} ) of The distance (mm) in the thickness direction from the surface on one side to the surface on the other side when O is 0, E (y) is the elastic modulus at y of the laminated sheet, and elastic modulus e0 is y = 0 (of the laminated sheet) mm)) elongation after bonding (dimensionless), e (y) is the free elongation before bonding of the material at y of the laminated sheet (dimensionless), and α (y) is the material at y of the laminated sheet. Linear expansion coefficient (1 / ° C.). Furthermore, since E (y) and e (y) are generally determined by the material, when the distance y in the thickness direction from the reference plane (y = 0) is in the i-th layer, E (y) = Ei, e (y ) = Ei. The stress and bending moment generated in the multilayer body by the thermal stress are given by simultaneous equations shown in Equation 5.

  The distribution of stress and bending moment in the two-layered multilayer body is as shown in FIGS. 4 and 5, respectively. Here, when Formula 5 is integrated with respect to y and no external force is applied, that is, F = 0 and M = 0, Formula 6 and Formula 7 are obtained.

F = e ₁ E ₁ t ₁ + e ₂ E ₂ t ₂ −e ₀ × (E ₁ t ₁ + E ₂ t ₂ ) − (θ / 2) × (E ₁ × t ₂ ² −E ₂ × t ₁ ² + E ₂ × (t ₁ + t ₂ ) ² ) = 0 (6)

_{M = ((e 1 E 1} × t 1 2 -e 2 E 2 × t 1 2 + e 2 E 2 × (t 1 + t 2) 2) -e 0 × (E 1 × t 1 2 -E 2 × t ₁ ² + e ₂ × (t ₁ + t ₂ ) ² )) / 2− (θ / 3) × (E ₁ × t ₁ ³ −E ₂ × t ₁ ³ + E ₂ × (t ₁ + t ₂ ) ³ ) = 0 ... (7)

In the simultaneous equations of Equations 6 and 7, when e ₀ is eliminated and the curvature θ is solved, Equation 8 is obtained.

θ = −6E ₁ E ₂ (e ₁ −e ₂ ) × t ₁ t ₂ (t ₁ + t ₂ ) / (E ₁ ² t ₁ ⁴ + E ₂ ² t ₂ ⁴ + 2E ₁ E ₂ t ₁ t ₂ (2t ₁ ² + 3t ₁ t ₂ + 2t ₂ ² )) (8)
The free elongation e _i caused by the temperature difference ΔK is expressed by Equation 9 if the linear expansion coefficient of the i-th layer is α _i .

e _i = α _i × ΔK (9)
Since ε = θ / ΔK where ε is the rate of change of curvature with respect to temperature, ε is expressed by Equation 10 from Equation 8 and Equation 9.
ε = −6E ₁ E ₂ (α ₁ −α ₂ ) × t ₁ t ₂ (t ₁ + t ₂ ) / (E ₁ ² t ₁ ⁴ + E ₂ ² t ₂ ⁴ + 2E ₁ E ₂ t ₁ t ₂ (2t ₁ ² + 3t ₁ t ₂ + 2t ₂ ² )) ... (10)
Unless otherwise specified in this specification, the curvature change rate ε is a value obtained by calculation.

The smaller the value of the curvature change rate ε with respect to the temperature, the smaller the warp caused by the temperature change. Therefore, it is ideal to set ε = 0. In this case, theoretically, no warp due to temperature occurs. However, since t ₁ , t ₂ , E ₁ , and E ₂ are all positive constants, ε = 0 only when α ₁ = α ₂ . Since α ₁ and α ₂ are determined according to the respective materials, α ₁ = α ₂ is not usually satisfied when ε ₁ and α ₂ are made of different materials, so ε = 0 cannot be established. Therefore, it is necessary to change the plate thickness, elastic modulus, and linear expansion coefficient so as to make ε as small as possible. However, since the change in the elastic modulus and the linear expansion coefficient generally involves a change in the material, it is difficult to greatly change the elastic modulus and the linear expansion coefficient when the material is determined to some extent by optical design. When the thickness of the layer is determined for thinning, the curvature change rate ε can be reduced by increasing the ratio of the layer thickness. For example, when the thickness of the MS is limited to 2 mm, the value of the curvature change rate ε can be reduced by reducing the thickness of the PET film as the other layer as much as possible. Table 1 shows the change in curvature change rate ε when the thickness of the MS is fixed at 2 mm and the thickness of the PET film is changed.

表１はＰＥＴフィルムの厚さを０．０５ｍｍ、０．１ｍｍ、０．２ｍｍ、０．３ｍｍとして曲率変化率εを計算した結果を示している。ここＰＥＴの弾性率を４０００ＭＰａ、線膨張率３×１０^−５（１／℃）とし、ＭＳの弾性率を３０００ＭＰａ、線膨張率は７×１０^−５（１／℃）として計算した。以上の４条件ではＰＥＴフィルムの厚みが０．０５ｍｍの時、曲率変化率εが最小で、０．３ｍｍの時最大となる事がわかる。この曲率変化率における温度と曲率の関係を図３に示す。ここでは２０℃の時の曲率を０としている。ＰＥＴフィルムの厚みが０．０５ｍｍの時、温度変化による曲率が小さく、反りによる画像、画質の劣化が抑制されるようになる。

Table 1 shows the results of calculating the curvature change rate ε when the thickness of the PET film is 0.05 mm, 0.1 mm, 0.2 mm, and 0.3 mm. Here, the elastic modulus of PET was 4000 MPa, the linear expansion coefficient was 3 × 10 ⁻⁵ (1 / ° C.), the elastic modulus of MS was 3000 MPa, and the linear expansion coefficient was 7 × 10 ⁻⁵ (1 / ° C.). Under the above four conditions, it can be seen that the curvature change rate ε is minimum when the thickness of the PET film is 0.05 mm and maximum when the thickness is 0.3 mm. The relationship between the temperature and the curvature at this curvature change rate is shown in FIG. Here, the curvature at 20 ° C. is assumed to be zero. When the thickness of the PET film is 0.05 mm, the curvature due to the temperature change is small, and the deterioration of the image and the image quality due to warpage is suppressed.

  As described above, the applicant of the present application has found that the refractive index of curvature ε can be reduced by combining the linear expansion coefficient, thickness, and elastic modulus parameters of each layer of the two-layer structure based on Equation 7. . The warpage can be reduced by designing the linear expansion coefficient, thickness, and elastic modulus of each layer so as to reduce the curvature change rate ε. Even when there is a restriction on any of the linear expansion coefficient, thickness, and elastic modulus, warping can be reduced by comprehensively designing the values of the linear expansion coefficient, thickness, and elastic modulus. For example, even when a material having greatly different linear expansion coefficients has a multilayer structure, the warpage due to temperature change can be reduced by adjusting the thickness or elastic modulus. Furthermore, even when the overall thickness is limited due to the demand for thinning or when the thickness of one layer is determined, other parameters can be adjusted so that the curvature change rate ε becomes small. . By designing and manufacturing a sheet for a rear projection type screen in this way, dissimilar materials that have been difficult to use in combination due to deterioration in image and image quality are used for the sheet for the rear projection type screen. Is possible.

  Next, a three-layer laminated sheet in which a front plate with a PET film is bonded to a lenticular lens will be described with reference to FIG. The same reference numerals as those in FIG. 1 and FIG. Further, the overall configuration of the rear projection type screen is the same as that shown in FIG. In the present embodiment, the front plate 3 with the PET film 4 is attached to the external light absorbing layer 14 of the lenticular lens sheet 1. A method for reducing the warpage caused by the temperature change in such a three-layer structure will be described.

  The present invention can prevent deterioration of image and image quality due to warping even in a combination of materials having a different coefficient of thermal expansion and likely to be deformed due to temperature change in a three-layered multilayer body as shown in FIG. . Even in a three-layer structure, the curvature θ can be obtained by solving the simultaneous equations of Equation 5 described above. The calculation formula in the case of three layers is shown in Formula 11.

θ = −6 (E ₁ E ₂ (e ₁ −e ₂ ) (t ₁ ² t ₂ + t ₁ t ₂ ² ) + E ₁ E ₃ (e ₁ −e ₃ ) (t ₁ ² t ₃ + 2t ₁ t ₂ t ₃ + t ₁ t ₃ ² ) + E ₂ E ₃ (e ₂ −e ₃ ) (t ₂ ² t ₃ + t ₂ t ₃ ² )) / (E ₁ ² t ₁ ⁴ + E ₂ ² t ₂ ⁴ + E ₃ ² t ₃ ⁴ + 2E ₂ E ₃ t ₂ t ₃ (2t ₂ ² + 3t ₂ t ₃ + 2t ₃ ² ) + 2E ₁ E ₂ t ₁ t ₂ (2t ₁ ² + 3t ₁ t ₂ + 2t ₂ ² ) + 2E ₁ E ₃ t ₁ t ₃ 2t ₁ ² + 3t ₁ t ₃ + 2t ₃ ² ) + 12E ₁ E ₃ t ₁ t ₂ t ₃ (t ₁ + t ₂ + t ₃ )) (11)
Therefore, from Equations 9 and 11, the curvature change rate ε due to temperature change is expressed by Equation 12 as a function of the elastic modulus Ei, plate thickness t _i, and linear expansion coefficient α _i of each layer.

ε = −6 (E ₁ E ₂ (α ₁ −α ₂ ) (t ₁ ² t ₂ + t ₁ t ₂ ² ) + E ₁ E ₃ (α ₁ −α ₃ ) (t ₁ ² t ₃ + 2t ₁ t ₂ t ₃ + t ₁ t ₃ ² ) + E ₂ E ₃ (α ₂ −α ₃ ) (t ₂ ² t ₃ + t ₂ t ₃ ² )) / (E ₁ ² t ₁ ⁴ + E ₂ ² t ₂ ⁴ + E ₃ ² t ₃ ⁴ + 2E ₂ E ₃ t ₂ t ₃ (2t ₂ ² + 3t ₂ t ₃ + 2t ₃ ² ) + 2E ₁ E ₂ t ₁ t ₂ (2t ₁ ² + 3t ₁ t ₂ + 2t ₂ ² ) + 2E ₁ E ₃ t ₁ t ₃ 2t ₁ ² + 3t ₁ t ₃ + 2t ₃ ² ) + 12E ₁ E ₃ t ₁ t ₂ t ₃ (t ₁ + t ₂ + t ₃ )) (12)

  The numerator of Expression 12 is constituted by the sum of three terms. It is desirable that at least one of the three terms has a positive sign and at least one term has a negative sign. Then, by setting the absolute values of the positive term (the sum when there are two positive terms) and the negative term (the sum when there are two negative terms) to substantially the same value, the rate of curvature change ε can be reduced. In this way, a material that can reduce the curvature change rate ε is selected, and the thickness is determined. And the value of (epsilon) can be made small by setting it as the layer structure arrangement | positioning based on the selected material and thickness. Thereby, it is possible to prevent the deterioration of the image and the image quality due to the temperature change. In order to realize such a layer configuration, three values of the linear expansion coefficient, thickness, and elastic modulus of each layer, that is, a total of nine parameters can be changed. Therefore, even if any parameter cannot be changed or cannot be changed greatly due to various restrictions, the value of the curvature change rate ε can be reduced by adjusting other parameters.

For example, in the multilayer shown in FIG. 7, the linear expansion of the lenticular lens 1 is made with the thickness of the front plate 3 being 2 mm, the thickness of the PET film 4 being 0.05 mm, and the thickness of the lenticular lens 1 being 0.7 mm. The simulation result when the rate is changed is shown. Here, the physical properties of the front plate 3 and the PET film 4 are set to the same values as described above, and the linear expansion coefficients of the lenticular lenses are 6.0 × 10 ⁻⁵ , 6.4 × 10 ⁻⁵ , 6.8 ×. The simulation is performed with 10 ⁻⁵ (1 / ° C.). The material of the lenticular lens 1 is MS, and the linear expansion coefficient can be adjusted by MS molar ratio, polymerization degree, crystallinity, elastomer modification, various additives, and the like. At this time, the elastic modulus may slightly change with the adjustment. In the present invention, the above-described exact elastic modulus values are applied. However, the elastic modulus is set to 3200 MPa for the sake of simplicity of explanation only in the simulations related to FIGS. FIG. 8 is a diagram showing the relationship between temperature and curvature, in which the horizontal axis represents temperature (° C.) and the vertical axis represents curvature (1 / mm). As shown in FIG. 8, when the linear expansion coefficient of the lenticular lens 2 is 6.4 × 10 ⁻⁵ , deformation due to temperature is substantially eliminated.

  The warpage can be reduced by designing the linear expansion coefficient, thickness, and elastic modulus of each layer so as to reduce the curvature change rate ε. Even when there is a restriction on any of the linear expansion coefficient, thickness, and elastic modulus, the warpage can be reduced by designing the values of the linear expansion coefficient, thickness, and elastic modulus as a whole. Even when there are various limitations such as a thickness limitation due to a demand for thinning and a material limitation due to optical design, it is possible to suppress degradation of the image and image quality of the rear projection screen.

It is more effective to use the above method with a three-layer structure than with a two-layer multilayer. When trying to reduce the curvature change rate in a two-layer structure, since there are few parameters that can be changed, warping may not be sufficiently reduced due to various limitations. However, in the case of three layers, there are many parameters that can be changed, and further, depending on the combination of each parameter, it is possible to reduce the number of molecules in the formula 12 to 0, so that it is theoretically possible to eliminate the warp. Furthermore, the above-described method is not limited to a two-layer or three-layer multilayer body, and can be used for a multilayer body having four or more layers. That is, the curvature change rate ε can be calculated by solving the simultaneous equations with F = 0 and M = 0 in Formula 5 as in the above embodiment. In this case, in the case of the n layer, the parameter for reducing the curvature change rate ε is 3n, which is effective because it further increases. Further, the curvature change rate ε can be set to 0 depending on the combination of each parameter.
The design method according to the present invention can be used for, for example, a two-layer lenticular sheet, a two-layer Fresnel, a three-layer Fresnel, a multilayer front plate, a front plate integrated lenticular sheet, a front plate integrated lenticular sheet with an antireflection film, and the like. is there. Of course, it is not limited to these. A multilayer body in which the material of each layer is different may be used. It is also possible to calculate the adhesive or pressure sensitive adhesive as one layer. Table 2 shows physical property values of typical materials used for the sheet used for the rear projection type screen.

この値を用いることによって、反りが小さくなるように設計することができる。表２に示した材質は背面投射型スクリーンのシートに用いられる代表的な材質であるが、これに限られるものではない。それぞれの材質の物性値は代表的な例であり、同じ材質であっても示した値に限られるものではない。例えば、上記の材料に添加物を添加した場合、添加物の種類や濃度によって、物性値が変化するのは明らかである。なお、上述の実施の形態では各層を貼り合せた複層体を用いたが、本発明にかかる設計方法は成形により一体的に形成された複層体でも利用可能である。

By using this value, it is possible to design the warp to be small. The materials shown in Table 2 are typical materials used for the sheet of the rear projection screen, but are not limited thereto. The physical property values of the respective materials are representative examples, and even the same material is not limited to the values shown. For example, when an additive is added to the above material, it is clear that the physical property value changes depending on the type and concentration of the additive. In the above-described embodiment, a multilayer body in which each layer is bonded is used. However, the design method according to the present invention can also be used for a multilayer body integrally formed by molding.

Since a multilayer body made of a material having substantially the same linear expansion coefficient has substantially the same elongation due to a temperature change, the stress is small and warping does not occur so much. However, since the multi-layered bodies made of materials having different linear expansion coefficients have different elongation rates, warping due to stress increases. Therefore, it is effective to use the above-described design method for a multilayer body made of materials having different linear expansion coefficients. For example, α _{max is the} coefficient of linear expansion of a multilayer body in which the linear expansion coefficient of the layer having the largest linear expansion coefficient differs from the linear expansion coefficient of the minimum layer by 5% or more, that is, the layer having the largest linear expansion coefficient And when the linear expansion coefficient of the layer having the minimum linear expansion coefficient is α _min , it is preferable to use it for a sheet made of a multilayer body that satisfies the condition of (α _max −α _min ) / α _max ≧ 0.05. It is. Using a material with a linear expansion coefficient different by 5% or more for the rear projection type screen is difficult when the thickness is limited, but can be easily used by the method described above.

Even when the elastic modulus of each layer is substantially the same, the bending stress generated in the multilayer body is weak, so the amount of warpage is small. Therefore, the present invention is preferably used for a multilayer body in which the elastic modulus of each layer is different. For example, let E _max be the elastic modulus of a multi-layer body in which the elastic modulus of the layer having the maximum elastic modulus differs from the elastic modulus of the minimum layer by 10% or more, that is, the layer having the maximum elastic modulus in the multi-layer body, and When the elastic modulus of the layer having a modulus is E _min , it is preferable to use it for a sheet made of a multilayer body that satisfies the condition of (E _max −E _min ) / E _max ≧ 0.1. It has been difficult to use a material having an elastic modulus different by 10% or more for the rear projection type screen when the thickness is limited, but it can be easily used by the method described above. The design method according to the present invention may be used for any material, but is desirably used when the elastic modulus is limited. In particular, it is difficult to use a material having an elastic modulus of 10,000 MPa or less for each layer when there is a limitation on the thickness or the like, but by the method described above, a material having an elastic modulus of 10,000 MPa or less can be easily used. became. Thereby, warpage due to temperature change can be reduced, and deterioration of image quality can be prevented.

Similarly, when the difference in the thickness of each layer is greatly different, the bending stress generated in the multilayer body is weak, so that the amount of warpage becomes small. Accordingly, the present invention is preferably used for a multilayer body in which the difference in thickness between the layers is small. For example, when the ratio of the thickness of the thickest layer to the thinnest layer is 200 times or less, that is, when the thickness of the thickest layer is t _max and the thickness of the thinnest layer is t _min , (t _max / T _min ) ≦ 200 is effective for use in a multilayer body. It was difficult to use a multilayer body having a thickness ratio of 200 times or less for a rear projection type screen when there was a limitation on the thickness, etc., but it became possible to use it easily by the method described above. . In the present invention, the sheet thickness is not limited, but is desirably used when the total thickness is limited, for example, when the total thickness of the sheet is 8 mm or less.

  Furthermore, although it was very difficult to use a combination satisfying two or more of the conditions of linear expansion coefficient, elastic modulus, and thickness (conditions for increasing warpage), it was easily realized by the present invention. This makes it possible to reduce warpage even when using a multilayer sheet combining materials and thicknesses that would increase warpage in the past, resulting in deterioration of the image and image quality of the rear projection screen. It becomes possible to prevent.

The present applicant performs various tests on the sheet whose curvature change rate ε is calculated by the above-described method, and the curvature change rate ε (1 / mm ° C.) is −7.0 × 10 ⁻⁶ ≦ ε ≦ 7.0 ×. It has been found that 10 ⁻⁶ suppresses deterioration of image and image quality even with respect to a temperature change caused by actual use. The curvature change rate ε is preferably −5.0 × 10 ⁻⁶ ≦ ε ≦ 5.0 × 10 ⁻⁶ , and more preferably −3.0 × 10 ⁻⁶ ≦ ε ≦ 3.0 × 10 ^−6. If so, the deterioration of the image and image quality is further suppressed, and the display characteristics of the rear projection screen can be improved. Needless to say, it is desirable that ε = 0 calculated ideally. In this way, the material and thickness for reducing the value of ε can be selected. In addition, the example of the result of having tested in the following Examples is demonstrated.

Also, the curvature change rate ε of the screen can be reduced by setting it on the display frame. Since the curvature change rate ε described above is a value when the frame is not set, if the curvature change rate when the frame is set is εf (1 / mm ° C.), there is usually a relationship of ε / εf = 2-5. Therefore, if expressed as ε / εf = 2, −3.5 × 10 ⁻⁶ ≦ εf ≦ 3.5 × 10 ⁻⁶ , desirably −2.5 × 10 ⁻⁶ ≦ εf ≦ 2.5 × 10 ⁻⁶ , and more desirably −1.5 × 10 ⁻⁶ ≦ εf ≦ 1.5 × 10 ⁻⁶ . As described above, the linear expansion coefficient, that is, the difference in expansion coefficient depending on the temperature has been described. However, the present invention may be similarly applied to the difference in expansion coefficient due to moisture absorption.

Example 1.
In this example, evaluation was performed by changing the environmental temperature between a sheet manufactured to reduce warpage and a conventional sheet by the method described in the embodiment. In this example, a 100 μm-thick antistatic PET film was bonded with a photo-curing adhesive to an elastomer-modified MS 2 mm-thick front plate whose linear expansion coefficient and elastic modulus were adjusted so as to reduce warpage. Further, an MS2 wrench having a pitch of 0.52 was adhered to the other surface of the front plate at the non-light-collecting portion and integrated. The sheet size was 50 inches.

  On the other hand, in the comparative example according to the prior art, an MS 2 mm thick front plate is bonded with a 100 μm thick antistatic PET film photocurable adhesive. Further, a 0.52 pitch MS wrench made of elastomer-modified MS as a main raw material was bonded to the other surface of the front plate at its non-light-collecting portion and integrated. The sheet size was 50 inches. That is, an example in which materials of the lenticular sheet and the front plate are different will be compared with Example 1 as Comparative Example 1.

  Table 3 shows simulation results and actual measurement data for the physical property values of the materials used in Example 1 and Comparative Example 1.

このように実施例１の曲率変化率は比較例１の曲率変化率と比べて、非常に小さい値であった。

Thus, the curvature change rate of Example 1 was a very small value compared with the curvature change rate of Comparative Example 1.

  These front plate integrated wrenches were set on a CRT type rear projection TV, and the environmental temperature was changed to 0 to 40 ° C. for evaluation. A Fresnel lens sheet was provided on the back side (light incident side) of the sheet, and the amount of float from the Fresnel lens sheet at the center of the screen was measured. The Fresnel lens sheet was formed of a single material, and the one having a deformation amount of 0 mm at the center at 0 to 40 ° C. was used. Further, after visually confirming the deterioration of the image and image quality, it was removed from the TV set, and the curvature change rate was measured.

The float amount of the Fresnel and the integrated wrench in the temperature range of 0 to 40 ° C. in Example 1 was −0.5 mm. As a result of visual confirmation, no image shift or image quality deterioration such as color shift or resolution reduction occurred. On the other hand, the floating amount of the Fresnel and the integrated wrench in the temperature range of 0 to 40 ° C. in Comparative Example 1 was 20 mm, and image degradation such as a significant resolution reduction and coloring occurred. The measured value of the rate of change in curvature when removed from the TV set was 8.0 × 10 ⁻⁶ , which was similar to the calculated value. In this way, using the above-described design method, a front projection plate having a two-layer structure and its material was changed to obtain a rear projection screen in which image and image quality deterioration due to temperature change was prevented.

Example 2
In Example 2, degradation of an image and image quality due to temperature change was evaluated for a rear projection type project screen created by the above-described method. A film wrench having a thickness of 175 mm having a cylindrical lens formed by extrusion molding was bonded to an MS plate containing a diffusion material having a thickness of 2 mm using a photocurable adhesive. Further, an antireflection film (AR film) having a thickness of 0.1 mm was adhered to the opposite surface side (light-emitting surface side) of the front plate to obtain a rear projection screen for LCD in which the wrench, front plate and AR film were integrated. . According to the simulation, this screen sheet had a curvature change rate ε of 3.0 × 10 ⁻⁶ (1 / mm ° C.). Table 4 shows simulation results and actual measurement data for the physical property values of the materials used in Example 2.

This screen was set on a rear projection TV for LCD, the environmental temperature was changed to 0 to 40 ° C., the focal position variation was confirmed, and the deterioration of the image was visually confirmed. Then, it removed from TV set and the curvature change rate was measured. In the temperature range of 0 to 40 ° C., there was no fluctuation of the focal position, and a good screen that did not deteriorate the image was obtained. The actual measurement value of the curvature change rate at this time was 2.6 × 10 ⁻⁶ (1 / mm ° C.), which was substantially the same as the calculated value. Thus, by the above-described method, it was possible to obtain a rear projection screen in which warpage due to temperature change was small and deterioration in image and image quality was suppressed.

Example 3 FIG.
In Example 1 and Example 2, the three-layer configuration is used. Next, a simulation result of an example in which warpage is reduced by adopting a configuration of four or more layers will be described with reference to FIG. FIG. 9A is a cross-sectional view showing the configuration of Example 3, and FIG. 9B is a cross-sectional view showing the configuration of Comparative Example 3. In Example 3, a 0.1 mm thick PET film is used as a base material, a photocurable resin is applied to the surface, and a cylindrical lens is provided by a photocuring reaction to form a lenticular lens sheet. A 2 mm-thick two-layer front plate is bonded to the lenticular lens sheet via an adhesive sheet. The 50-inch size LCD screen consisting essentially of five layers was modified by the above-described method to change the structure of the two-layer front plate so that the warpage due to temperature changes was reduced. Here, the thickness of the first layer of the two-layer front plate is 1.67 mm, and the thickness of the second layer is 0.33 mm.

  On the other hand, as a comparative example, it was set as the same structure except having used the thing of 1 layer structure of 2 mm thickness as a front plate. Therefore, the total thickness of all layers was the same. This 50-inch LCD screen consisting essentially of four layers was designated as Comparative Example 3. Table 5 shows the physical property values and simulation results of the materials used in Example 3 and Comparative Example 3.

The calculation result of the curvature change rate ε of Example 3 is −0.13 × 10 ⁻⁶ (1 / mm ° C.). On the other hand, the calculation result of the curvature change rate ε of Comparative Example 3 was 5.3 × 10 ⁻⁶ (1 / mm ° C.). Even if the material and thickness of the lenticular lens sheet and the front plate are limited as described above, the temperature can be adjusted by adjusting the thickness ratio and physical properties of a specific layer as a multi-layer structure composed of different physical properties. Warpage due to change can be suppressed, and deterioration of image and image quality can be prevented.

It is a perspective view which shows the structure of the rear projection screen concerning this invention. It is a side view which shows the structure of the front board concerning this invention. It is a perspective view which shows the state which the curvature produced in the two-layer structure. It is sectional drawing which shows distribution of the stress which generate | occur | produces in a two-layer structure. It is sectional drawing which shows distribution of the bending moment which generate | occur | produces in a two-layer structure. It is a figure which shows the relationship between the temperature and curvature of a front plate concerning this Embodiment. It is sectional drawing which shows the structure of the lenticular lens sheet concerning this Embodiment. It is a figure which shows the relationship between the temperature of a lenticular lens sheet, and a curvature. It is sectional drawing which shows the structure of the multilayer body concerning Example 3 of this invention.

Explanation of symbols

1 Lenticular lens sheet, 2 Fresnel lens sheet, 3 Front plate, 4 PET film, 11 Lenticular lens,
12 condensing part, 13 non-condensing part, 14 outside light absorption layer

Claims (4)

A laminated sheet having a multilayer structure that is asymmetric in the thickness direction of n layers (n is a natural number of 3 or more),
The linear expansion coefficient of the layer having the minimum linear expansion coefficient relative to the linear expansion coefficient of the layer having the maximum linear expansion coefficient of the laminated sheet is 95% or less;
The elastic modulus of each layer of the laminated sheet is within 10,000 MPa, and the elastic modulus of the layer having the minimum elastic modulus with respect to the elastic modulus of the layer having the maximum elastic modulus is 90% or less,
The thickness of the thickest layer of the laminated sheet is within 200 times the thickness of the thinnest layer,
The curvature change rate ε (1 / mm ° C.) with respect to the temperature change ΔK of the laminated sheet, calculated by the following simultaneous equations, is −7.0 × 10 ⁻⁶ ≦ ε ≦ + 7.0 × 10 ⁻⁶ . A laminated sheet.

(The curvature (1 / mm) after the lamination of the laminated sheets is θ, the plate thickness (mm) of the i-th layer (i = 1, 2,... N) of the laminated sheets is t _i , and the laminated sheets The one-side surface of the sheet is 0, the distance (mm) in the thickness direction from the one-side surface to the opposite-side surface is y, the elastic modulus at y of the laminated sheet is E (y), and y = 0 ( mm) is the elongation after bonding (dimensionless), e0, the free elongation before bonding of the material at y in the laminated sheet (dimensionless) is e (y), and the linear expansion coefficient of the laminated sheet at y is the material. (1 / ° C) is assumed to be α (y).)   A rear projection screen using the laminated sheet according to claim 1. A design method for designing the material and thickness of each layer of a laminated sheet having a multilayer body that is asymmetric in the thickness direction of n layers (n is a natural number of 3 or more),
The linear expansion coefficient of the layer having the minimum linear expansion coefficient relative to the linear expansion coefficient of the layer having the maximum linear expansion coefficient of the laminated sheet is 95% or less;
The elastic modulus of each layer of the laminated sheet is within 10,000 MPa, and the elastic modulus of the layer having the minimum elastic modulus with respect to the elastic modulus of the layer having the maximum elastic modulus is 90% or less,
The thickness of the thickest layer of the laminated sheet is within 200 times the thickness of the thinnest layer,
The curvature (1 / mm) after the lamination of the laminated sheets is θ, the plate thickness (mm) of the i-th layer (i = 1, 2,... N) of the laminated sheets is t _i , The one-side surface is 0, the distance (mm) in the thickness direction from the one-side surface to the opposite-side surface is y, the elastic modulus at y of the laminated sheet is E (y), and y = 0 (mm ) Is the elongation after bonding (dimensionless) e0, the free elongation of the material before bonding of the laminated sheet y (dimensionless) is e (y), and the linear expansion coefficient of the laminated sheet y at the material ( 1 / ° C) is α (y),
Eliminating e0 in the simultaneous equations shown below and solving for curvature θ;

Calculating a curvature change rate ε as a function of the elastic modulus E _{i of} each layer, the plate thickness t _i and the linear expansion coefficient α _i based on the curvature θ obtained from the simultaneous equations;
Determining the elastic modulus E _i , the plate thickness t _i and the linear expansion coefficient α _i of each layer so that the curvature change rate ε is −7.0 × 10 ⁻⁶ ≦ ε ≦ + 7.0 × 10 ⁻⁶ ; A method for designing a laminated sheet comprising: Producing a laminated sheet designed by the laminated sheet designing method according to claim 3;
A method of manufacturing a rear projection type screen, comprising a step of fixing the laminated sheet to a frame.

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