KR100538482B1 - Resin composition for lens sheet, lens sheet, and projection screen - Google Patents

Abstract

The present invention defines a mechanical property in consideration of the pressure and time factor actually applied to the ionized irradiation curable resin composition, so that a lens sheet can be obtained without causing breakage of the lens shape even if any input is applied to the lens sheet surface. A resin composition, a lens sheet, and a projection screen are provided. The lens sheet has a compressive modulus greater than 0 MPa and less than 840 MPa, a creep strain factor greater than 0% and less than 57%, or a compressive modulus greater than 840 MPa and less than 3500 MPa, and a creep strain factor greater than 10% When the large and less than 20% ionized irradiation curable resin composition or E (MPa) represents the compressive modulus and C (%) is the creep strain factor, the following relationship: C <-2 × 10 ^-2 E + 63, and C It is molded using an ionized irradiation curable resin composition having a compressive elastic modulus and a creep strain factor satisfying> -2.6 × 10 ⁻³ E + 3.

Description

Resin composition for lens sheet, lens sheet and projection screen {RESIN COMPOSITION FOR LENS SHEET, LENS SHEET, AND PROJECTION SCREEN}

The present invention relates to an ionizing radiation curable resin composition for forming a lens sheet such as a Fresnel lens sheet, a lens sheet in which a lens portion is formed using the composition, and a projection screen on which the lens sheet is mounted. will be.

Until now, the two-sheet structure of the projection screen manufactured by combining a lenticular lens and a Fresnel lens was common as a projection screen. In this structure, in order to bond the two lenses to each other, as shown in FIG. 1, the planar Fresnel lens sheet is formed of a lenticular lens sheet that is bent in advance by pressing the lenticular lens sheet against the Fresnel lens sheet. In combination. Thus, pressure is generated at the contact portion between the two lens sheets forming the combination. For example, as shown in FIG. 6, in the case of a screen in which the lens surface of a lenticular lens in which a ridge is formed vertically is superimposed on the lens surface of a circular Fresnel lens, linear contact is mainly performed at the left and right portions of the screen. line contact occurs, and point contact occurs mainly in the vertical direction of the screen. In such a projection screen, the Fresnel lens sheet side opposite to the lenticular lens sheet is arranged concentrically with portions having a substantially triangular cross section and respective vertices with an acute angle. On the lenticular lens sheet side opposite to the Fresnel lens sheet, the cross-sectional shape is formed in a semi-circular-columnar shape. Therefore, the material (resin composition) forming the lens surface of the Fresnel lens having an acutely forward facing end at an acute angle at the contact portion must have a mechanical property of greater than a predetermined value for crush. This is because a good image cannot be obtained if the lens surface is easily broken by the above-mentioned pressure when using the lens sheet as a projection screen.

Regarding the above-mentioned problem, Japanese Patent Laid-Open No. 10-10647 discloses an elastic modulus of the active energy ray-curable resin used in the lens portion of the lens sheet at 80 to 20,000 kg / cm 2 at a temperature range of -20 ° C to + 40 ° C. By setting it to the range, the lens sheet which is excellent in shape stability over a wide temperature range and which can maintain an optical characteristic is proposed.

In addition, Japanese Patent Application No. 2000-036435 discloses a dissipation factor tanδ of dynamic visco-eleasticity after curing of the ionized irradiation curable resin constituting the lens in consideration of the case where a dynamic force is applied to the lens sheet. By setting so that it may fall within a predetermined range, there is provided a resin composition for a lens sheet which does not accumulate stress therein and has flexibility and good restoring force.

However, in the specification of Japanese Patent Laid-Open No. 10-10647, the elastic modulus defined in JIS K-7113 is adopted. Since this elastic modulus is obtained by determining the value of the tensile elastic modulus using a flat film, it cannot be said that it is reliably reproduced in an environment in which an ionized irradiation curable resin is actually used (compressed).

In addition, the duration of the pressure generated between the two lenses is very long when the resin composition is actually used as a projection screen. That is, it has a restoring force which acts so that a part of resin composition for lenses may return said pressure gradually. Therefore, when designing and selecting a resin composition for a lens, it is necessary to take into account the temporal factors that must be included in the mechanical properties of the resin composition.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing three aspects each illustrating a state of manufacturing a screen by assembling a lenticular lens sheet into a Fresnel lens sheet.

2 is a graph illustrating a load / intrusion-depth curve.

3 is a diagram illustrating a position at which an indenter is integrated into the sample lens.

4 is a graph illustrating the relationship between modulus of elasticity / creep strain factor for evaluation of failure.

FIG. 5 is a graph illustrating a range in which a lens that does not involve a problem of breakage can be obtained, considering only the relationship between the elastic modulus E and the creep strain factor C in FIG. 4.

FIG. 6 is a diagram illustrating three aspects, each illustrating a situation in which a contact portion occurs when the Fresnel lens and the lenticular lens overlap each other.

FIG. 7 is a graph estimating the load / integration depth curve obtained by performing a universal-hardness test.

Accordingly, the object of the present invention is to define the mechanical properties based on consideration of the pressure and time factors actually received by the ionizing radiation curable resin composition, so that even if an arbitrary pressure is applied to the surface of the lens sheet, the lens shape is reduced due to the pressure. It is to provide a projection screen using a lens composition, a lens sheet, and a lens sheet capable of obtaining a good image without damage.

Hereinafter, the present invention will be described in detail. In one aspect of the invention, the aforementioned problem is a lens of a lens sheet with a compression modulus of elasticity greater than 0 MPa and less than 840 MPa, and a creep deformation factor greater than 0% and less than 57%. It is eliminated by the ionization irradiation curable resin composition which forms a part.

In addition, in the second aspect of the present invention, the above-mentioned problem is directed to an ionized irradiation curable resin composition that forms a lens portion of a lens sheet having a compressive modulus of greater than 840 MPa and less than 3,500 MPa, and a creep strain factor of greater than -10% and less than 20%. Resolved by

In addition, in the third aspect of the present invention, the above-mentioned problem is solved when the compressive modulus is expressed as E (MPa) and the creep strain factor as C (%).

C <-2 × 10 ^-2 E + 63, and C> -2.6 × 10 ^-3 E + 3

It is solved by the ionization irradiation curable resin composition which forms the lens part of the lens sheet which has a compressive elastic modulus and a creep deformation factor which satisfy | fills.

According to each of the above features of the present invention, when used to mold the lens surface, even if an arbitrary pressure is applied to the surface of the lens sheet, the ionized irradiation curable resin capable of obtaining a good image without damaging the lens shape due to the pressure. A composition can be obtained.

In the fourth aspect of the present invention, a Fresnel lens sheet can be produced in which the lens sheet is formed of the ionizing radiation curable resin composition described in any one of the above-described features.

In a fifth aspect of the present invention, it is also possible to produce a projection screen on which a Fresnel lens sheet according to the above-described feature is mounted.

The above functions and advantages of the present invention will be apparent from the embodiments described below.

As a result of studying various test methods to measure mechanical properties additionally including the time factor of the ionized irradiation curable resin composition, the inventors found that a small grade (small grade) hardness measuring device is most suitable. In addition, by adopting the elastic modulus (E) and the creep strain factor (C) as specific measured values obtained by using the above-described small-grade hardness measuring device, the inventor of the present application is caused by the pressure received when used in the projection screen. It has been found that the ionized irradiation curable resin composition for Fresnel lens sheet can be selectively determined which can be used without any problems caused. Below, the small-grade hardness measuring device, the test sample preparation method, the measurement conditions, the measurement item, the damage evaluation on the Fresnel lens molded using the ionization irradiation curable resin composition used in the above-mentioned test, the measurement result of these tests, and Details of the results of his analysis will be explained in turn.

EXAMPLE

(1) small grade hardness measuring device

The small grade hardness measuring apparatus used in the embodiment of the present invention is a kind of universal hardness testing apparatus, which is commercially available as "Fisher 'scope H-100V" manufactured by Fisher. The device is intended to determine universal hardness by directly reading the indentation depth of the recess by forcing the indenter to the sample surface under a load of a predetermined magnitude. The inventor of the present application varied the load applied to the indenter in this test apparatus under predetermined conditions and measured various mechanical properties of the sample (resin composition). With this device, various properties can be measured (universal hardness HU, plasticity hardness HU _PLAST , flow properties, creep properties, properties of restoring properties of elasticity, etc.). In this test apparatus, a Vickers pyramid indenter with particularly high dimensional accuracy is used as the indenter, and as a result, the load / instrument depth curve as shown in FIG. 7 is measured. The measured data is processed by a computer mounted on the test apparatus, which results in a "elastic deformation straight line," as indicated by the broken line in the figure, and a "plastic deformation amount" hr ', which is expected therefrom and shows the depth of integration under test load. In addition, the relationship between universal hardness and the depth of instru- ment can be presented simply, as well as for the specifics of such theoretical interrelationships between the tested values in the monthly paper “Material-Testing Technology” Vol. 43, No. .2, April 1998 issue, and the book "Evaluation of Material Properties by Universal-hardness Test" (Cornelia Heermant, Dieter Dengel, Katayama Shigeo and Satoh Shigeo).

On the other hand, this test method is registered as "Testing Method on Metallic Materials" under the German test standard 50359-1. In addition, there is a proposed standard that is defined as an ISO standard and a committee draft for it was published in 1999.

(2) test sample preparation method

Ionized radiation curable resin compositions suitable as samples are coated in a Fresnel lens molding die to a thickness of 200 μm. At this time, the die temperature is maintained at a temperature of 40 to 42 ° C and the temperature of the resin is maintained at 42 ° C. Subsequently, the UV irradiation amount was 2000 mJ / cm 2 and the peak intensity was 250 mW / cm 2 using a molding lamp (metal halide lamp: manufactured by Japan Storage Battery Co., Ltd.) on the coated ionizing radiation curable resin composition as described above. The said resin composition is hardened by irradiating an ultraviolet-ray under conditions. It was then peeled off from the die and used as a test sample.

(3) measurement conditions

As described above, in the test for universal hardness, hardness is determined by reading the depth of recess of the recess while pressing the indenter to the sample surface with the indentation load applied to the indenter, and the inventor of the present application uses the indenter. Various mechanical properties of the sample resin composition were measured by gradually increasing or decreasing the indentation load on the basis of the indenter up or down to a predetermined value. As the indenter, a tungsten carbide ball having a diameter of 0.4 mm was used here. Hereinafter, specific measurement conditions will be described with reference to FIG. 2.

In Figure 2, point A indicates the state before starting the test. At this point A, the load (vertical axis) is not applied and has a value of zero, and the indentation depth (horizontal axis) of the indenter is also equal to zero. At point A, the forward end of the indenter bottom is slightly in contact with the sample surface. The position of the front end of the indenter lower end was set to be located at the center of the lens section length near 2 to 3 mm away from the center of the Fresnel lens sample while the position of the indenter was confirmed under the microscope (see FIG. 3).

From this state, the integral was divided into 100 steps at intervals of 0.1 second, and the load applied to the indenter was gradually increased until reaching 20 mN (from point A to point B in FIG. 2). In FIG. 2, point B represents the time of the maximum load Fmax (herein 20 mN) applied, ie the time of maximum deformation. By keeping the indenter under this load for 60 seconds, a so-called "creep deformation" occurred for the sample (point B to point C). In FIG. 2, the depth (C-B) μm of the integration represents the creep deformation amount. The indenter was then raised (point C to point D) at 40-second intervals until the minimum load (0.4 mN) of tester was reached over 40 steps. The indenter was held for 60 seconds (point D to point E) with the tester's minimum load (0.4 mN) applied. In FIG. 2, the depth (DE) μm of the intrusion represents the creep deformation amount when a minimum load is applied, and the depth (EA) μm of the integration represents the residual deformation amount, and also the depth (hmax-E) μm of the integration Denotes the amount of restored deformation.

The reason for applying the load to the sample resin composition by using the ball indenter is that the point of failure in the combination of the lenticular lens and the Fresnel lens is the point contact point where the lenticular lens is placed vertically and the shape of the Fresnel lens is placed horizontally. contact area, and therefore point load can reproduce the actual situation well. In addition, the reason why the maximum load Fmax is set to 20 mN is that the contact pressure between the two lenses is considerably low and it is difficult to actually measure it, so at the maximum deformation amount, the requirement to deform the reference resin to the range of 10 μm due to its displacement is required. This is because the condition is set to the maximum magnitude of the load. The reason why the maximum deformation amount is set to about 10 μm is described in Japanese Laid-Open Patent Publication No. 2000-155203, because "the deformation amount of the lens can be allowed because the light from the light source does not pass even if it is deformed up to 0.01 mm at the outer circumference part". Is based on the opinion (see paragraph [0018] of the publication).

(4) measurement items

The parameters that define the mechanical properties of the resin composition of the present invention, namely the elastic modulus (E) and the creep strain factor (C), can be analyzed from the above-described load displacement loop (FIG. 2). Here, by repeating the procedure described in the preceding item three times, the values of the elastic modulus (E) and the creep strain factor (C) obtained as the measurement items each time were averaged to obtain an arithmetic mean value. In this way these values were recorded as measured values.

The modulus of elasticity E and the creep strain factor C are expressed as follows.

(a) modulus of elasticity: E

E = 1 / (2 (hr (2R-hr)) ^1/2 ㆍ (hmax) Δh / ΔF- (1-νw) / Ew)

= 1 / (5.586.hr. (hmax) Δh / ΔF-7.813 × 10 ^-7 )

Where hr represents the intersection (in mm) of the tangent to the load displacement curve when the test load is at maximum (in mm, the area of decrease of load enclosed by C, D, hmax).

In addition, Δhmax / ΔF shows an inverse rise in the load displacement curve when the test load is at maximum (reduced region of the load surrounded by C, D, hmax in FIG. 2). The unit is mm / N.

In addition, vw represents the Poisson's ratio of tungsten carbide (Poisson's ratio) (= 0.22), Ew represents the elastic modulus of tungsten carbide (5.3 x 10 ⁵ N / mm 2), and R is the radius of the ball indenter (0.4 mm). ).

For reference, the elastic modulus E when the Vickers indenter (diamond) is used is expressed as follows.

E = 1 / (4tan (2 / α) hr. (Hmax) Δh / ΔF / π ¹ / ^2- (1-νdia) / Edia)

Where α represents the apex angle of the Vickers indenter, 136 °, νdia represents the Poisson's ratio of the diamond (= 0.25), and Edia represents the elastic modulus of the diamond (1.2 × 10 ⁶ N / mm 2) ).

(b) creep modification factor: C

C = (h2-h1) 100 / h1

In the above formula, h1 represents the depth of incidence when the load reaches a test load (here, 20 mN) held at a fixed value, and h2 represents a predetermined time elapsed while the test load is maintained as it is (Fig. 2). Point C) represents the depth of the integration. The unit is mm.

(5) Evaluation of the failure: Fresnel lens sheet molded from the ionized irradiation curable resin composition in which the elastic modulus (E) and the creep strain factor (C) were previously measured were combined with a predetermined number of lenticular lens sheets, and those 4 The sides were fixed using tape. Next, each assembly was inserted into a frame made of wood of a corresponding different TV size to make a TV set, and its white screen was visually observed. After 1 hour, each of the damaged Fresnel lens sheets was recorded with a "●" mark, and each of the Fresnel lens sheets identified as having no damage was recorded with a "○" mark (see Fig. 4).

(6) Test results: Table 1 shows the evaluation results for the breakage of the Fresnel lens sheet molded from the elastic modulus (Y) and the creep strain factor (C) of each of the ionized irradiation curable resin compositions, and the corresponding ionized irradiation curable resin composition. It shows in 1 in total. In addition, the elastic modulus (E) and the creep strain factor (C) are plotted along the lateral and longitudinal coordinate axes, and the evaluation results for the breakage in the test are indicated by "○" and "●" marks as described above in FIG. Indicates.

TABLE 1

(7) Analysis of test results: The inventor of the present application analyzed the test results described above, and as a result, came to the conclusions recognized as follows. First, the inventor classified the tested ionizing radiation curable resin composition into a group having a low elastic modulus (soft) and a group having a high elastic modulus (hard). In the case of the soft group, the inventors found that the modulus of elasticity E is greater than 0 MPa and less than 840 MPa and the creep strain factor is greater than 0% and less than 57%, preferably greater than 3% and less than 55%. Preferably, when the modulus of elasticity E is greater than 38 MPa and less than 412 MPa and the creep strain factor is greater than 3% and less than 55%, it has been found that a lens without problems associated with breakage can be obtained. Also, in the case of the hard group, when the elastic modulus E is greater than 840 MPa and less than 3500 MPa, and the creep strain factor is greater than -10% and less than 20%, more preferably greater than -6% and less than 20%. It has been found that the lens does not have a problem associated with breakage.

In addition, the inventors have relations, such as, to pay attention only when the relationship between the ionizing radiation-curing elastic modulus E and creep deformation factor of the resin composition ^{C: C <-2 × 10 -2} E + 63, and C> -2.6 × 10 It was found that the use of an ionized irradiation curable resin composition having ⁻³ E + 3 (the area enclosed by the straight lines m, n and E = 0 in FIG. 5) for molding can provide a lens free of problems associated with breakage.

In the above description, the ionized irradiation curable resin composition used to mold the Fresnel lens sheet used for the projection screen in combination with the lenticular lens sheet was described. However, the technical idea of the present invention is not limited thereto, and can be applied to any optical lens molded from another resin composition, in which the front end of the lens configuration is sharply formed and the front end portion under pressure applied in that direction is broken. have.

In addition, the present invention is not limited to the above-described embodiments, and suitable changes may be made without departing from or contradicting the subject matter or spirit of the present invention described in the claims and the entire specification. The resin composition for lens sheets, lens sheets, and projection screens obtained from such modifications are also included in the technical scope of the present invention.

As described above, molding is made into such an ionizing curable resin composition by setting the elastic modulus E and the creep strain factor C of the ionizing irradiation curable resin composition within a range between a predetermined value at a pressure and a value in consideration of the time factor. No matter what pressure is applied to the surface of the lens sheet, excellent images can be obtained without causing any breakage of the lens shape.

Claims (5)

Ionizing radiation curable that forms the lens portion of the lens sheet with a compression modulus of elasticity greater than 0 MPa and less than 840 MPa and creep deformation factor greater than 0% and less than 57%. Resin composition. An ionized irradiation curable resin composition that forms a lens portion of a lens sheet having a compressive modulus of greater than 840 MPa and less than 3500 MPa, and a creep strain factor of greater than -10% and less than 20%. When the compressive modulus is expressed as E (MPa) and the creep strain factor as C (%), the following relationship: C <-2 × 10 ^-2 E + 63, and C> -2.6 × 10 ^-3 E + 3 An ionized irradiation curable resin composition for forming a lens portion of a lens sheet having a compressive elastic modulus and a creep strain factor satisfying the above. A Fresnel lens sheet having a lens surface formed of the ionizing radiation curable resin composition of any one of claims 1 to 3. A projection screen on which the Fresnel lens sheet of claim 4 is mounted.