Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
148 words
A method for preparing a lithographic printing plate by a process comprising the steps of imagewise exposing a presensitized lithographic printing plate comprising a support having thereon a photosensitive layer and an ablatable light-shielding layer to a first light having a first wavelength to remove the imagewise exposed portion of the light-shielding layer by ablation, overall exposing the presensitized plate to a second light having a second wavelength to expose the photosensitive layer at portions in which the light-shielding layer has been removed and developing the overall exposed plate with a developer to remove the unremoved light-shielding layer and a non-imaging portion of the photosensitive layer to obtain the lithographic printing plate, wherein said light-shielding layer substantially cuts off the second light having the second wavelength to prevent a photochemical reaction from occuring in said photosensitive layer, said photosensitive layer photochemically reacting in response to the second light.
Claim 2
Dependent Claim
43 words
The method for preparing a lithographic printing plate of claim 1, wherein said light-shielding layer contains a light-heat converting substance capable of causing conversion of light into heat upon absorption of the first light and a substance capable of absorving the second light.
Claim 3
Dependent Claim
46 words
The method for preparing a lithographic printing plate of claim 1, wherein said light-shielding layer comprises a light-heat converting layer capable of converting light to heat upon absorption of the first light and a shielding layer capable of shielding said photosensitive layer from the second light.
Claim 4
Dependent Claim
26 words
The method for preparing a lithographic printing plate of claim 1, wherein said presensitized plate has an interlayer provided between said photosensitive layer and light-shielding layer.
Claim 5
Dependent Claim
40 words
The method for preparing a lithographic printing plate of claim 1, wherein said first light is a laser light having a power density of 100000 W/cm 2 or more, being exposed at an exposing speeed of 0.4 m/sec. or more.
Claim 6
Dependent Claim
18 words
The method for preparing a lithographic printing plate of claim 1, said second light is a ultraviolet radiation.
Claim 7
Dependent Claim
30 words
The method for preparing a lithographic printing plate of claim 1, wherein said first wavelength is not less than 500 nm and said second wavelength is less than 500 nm.
Claim 8
Dependent Claim
23 words
The method for preparing a lithographic printing plate of claim 1, wherein said light-shielding layer absorbs 80% or more of the first light.
Claim 9
Dependent Claim
23 words
The method for preparing a lithographic printing plate of claim 1, wherein said light-shielding layer absorbs 97% or more of the second light.
Claim 10
Dependent Claim
43 words
A presensitized lithographic printing plate comprising a support having thereon a photosensitive layer and an ablatable light-shielding layer is capable of absorbing a laser light and a light to which said photosensitive layer is sensitive, said light-shielding layer being water-soluble or aqueous alkali-soluble.
Claim 11
Dependent Claim
41 words
The presensitized lithographic printing plate of claim 10, wherein said light-shielding layer comprises a substance capable of absorbing a laser light, a substance capable of absorbing a light to which said photosensitive layer is sensitive, and water-soluble or aqueous alkali-soluble resin.
Claim 12
Dependent Claim
31 words
The presensitized lithographic printing plate of claim 11, wherein said light-shielding layer contains a near infrared absorbing dye as the substance capable of absorbing a laser light and a water-soluble resin.
Claim 13
Dependent Claim
19 words
The presensitized lithographic printing plate of claim 10, 11 or 12, wherein said photosensitive layer contains a o-quinonediazide compound.
Claim 14
Dependent Claim
19 words
The presensitized lithographic printing plate of claim 10, 11 or 12, wherein said photosensitive layer contains a diazo compound.
Claim 15
Dependent Claim
16 words
The presensitized lithographic printing plate of claim 12, wherein said near infrared absorbing dye is water-soluble.